Metabolic syndrome

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Metabolic syndrome is increasingly common but is affected by both age and ethnicity. The main risk factors include age and gender, being overweight, having high body fat percentage, having elevated levels of inflammatory biomarkers, low physical activity, greater time spent sedentary, smoking, lack of sleep, and depression. Exercise is beneficial for both the treatment and prevention of metabolic syndrome.

CONTENTS

What is metabolic syndrome?

Metabolic syndrome is a term that refers to a cluster of metabolic risk factors that put an individual at an increased risk for cardiovascular disease (CVD) and type II diabetes mellitus (T2DM). The most widely accepted risk factors that define metabolic syndrome are dyslipidaemia, elevated blood pressure and elevated plasma glucose. Metabolic syndrome is often referred to as an entity having a single cause. However, various researchers have more recently suggested that it truly is a syndrome, characterised by a grouping of cardiovascular risk factors and probably having more than one cause (Grundy et al., 2005). Moreover, although the various risk factors comprising metabolic syndrome increase the risk of developing CVD and increase all-cause mortality, the full syndrome is associated with a risk that is greater than the risk of each separate factor (Gami et al., 2007).


What is the prevalence of metabolic syndrome?

Various researchers have assessed the prevalence of metabolic syndrome including national population data, and specific to age and ethnicity. Between 1988 and 1994, the population of the United States with metabolic syndrome was estimated to be 47 million adults (Ford et al.) and a further 910,000 adolescents (Cook et al.). In recent years, the prevalence of metabolic syndrome seems to have increased. Data from the United States between 1999 and 2006, the prevalence is estimated to have increased by 6.2%, from 27.9% to 34.1% of US adults.

Study Method Finding
Ford et al. United States adults aged >20 years 21.8%
Ford et al. United States adults aged between 20-29 years 6.7%
Ford et al. United States adults aged between 60-69 years 43.5%
Ford et al. Mexican American adults aged >20 years 31.9%
Park et al. United States male adults aged >20 years 22.8%
Park et al. United States female adults aged >20 years 22.6%
Cook et al. United States adolescents aged 12-19 years 4.2%
Mozumdar et al. United States 34.1%
Gu et al. China male adults >20 years 9.8%
Gu et al. China female adults >20 years 17.8%
Tillin et al. UK White European male adults 18.8%
Tillin et al. UK White European female adults 9.1%
Tillin et al. UK South Asian male adults 46.3%
Tillin et al. UK South Asian male adults 30.8%
Tillin et al. UK African Caribbean male adults 26.7%
Tillin et al. UK African Caribbean female adults 26.4%
Hu et al. Europe male adults aged 30 – 89 years 15.7%
Hu et al. Europe male female adults aged 30 – 89 years 14.2%
Lim et al. Korea 31.3%
Park et al. Korea 15.7%
Rashdan et al. Kuwait 36.2%
Rojas et al. Mexico 36.8% – 49.8%
Misra et al. Asian Indian Americans 33.9%
Bener et al. Qatar 26.5% – 33.7%
Al-lawati et al. Oman 17%

Based on these studies, it appears that the prevalence of metabolic syndrome can range from 4.2% – 49.8% depending on the population studied. Older populations tend to display greater prevalence of metabolic syndrome than younger populations, as do non-white Caucasian adults compared to white and European adults.


What are the risk factors for metabolic syndrome?

A number of researchers have investigated the risks for metabolic syndrome from varying perspectives and have identified a large number of individual risks, as shown in the table below:

Study Method Finding
Bankoski et al. The researchers investigated the association between sedentary behaviour independent of physical activity in adults >60 years and metabolic syndrome. The researchers examined the data of 1,367 adults participating in the 2003 – 2006 National Health and Nutrition Examination Survey (NHANES) following the objective measure of sedentary time and duration of sedentary bouts using an accelerometer. The researchers found that people with metabolic syndrome spent more time being sedentary (67.3% vs. 62.2%) and took fewer breaks from being sedentary (82.3 vs. 87.6). These factors were both significantly associated with greater likelihood of metabolic syndrome.
Wijndaele et al. The researchers examined the association between sedentary behaviour and leisure time activity and the risk of metabolic syndrome in 992 adults aged >45 years. The researchers found that metabolic syndrome risk was associated with the time spent watching television and computer activities irrespective of physical activity level in women >45 years. Further, they found that moderate to vigorous physical activity was inversely associated with metabolic syndrome risk independent of time watching television and computer activities in both men and women >45 years.
Malik et al. The researchers performed a meta-analysis on the association between sugar-sweetened beverages and the risk of metabolic syndrome. They found in a pooled population of 19,431 participants, the intake of sugar-sweetened beverages of the highest quartile (1 – 2 servings per day) compared to the lowest (none or 1 serving/month) was associated with a 20% increase in the risk of metabolic syndrome.
Ford et al. The researchers examined the prevalence and correlates of metabolic syndrome in 3461 US adults participating in the 2003–2006 National Health and Nutrition Examination Survey (NHANES). The researchers found that metabolic syndrome was independently associated with age, hyperinsulinemia, hypercholesterolemia and C-reactive protein, and inversely associated with leisure time physical activity. Further, they found that men were at greater risk than women, as were African Americans and other non-white ethnic groups compared to white adults.
Karlsson et al. The researchers examined the association between metabolic risk factors (obesity, triglycerides and low concentrations of HDL-C) and shift work in 27,485 participants from the Västerbotten intervention program. The researchers found that obesity, high triglyceride levels and low concentrations of HDL-C seemed to occur together more often among shift workers compared to day workers.
Dunstan et al. The researchers examined the association between television viewing and physical activity participation in 6241 Australian adults >35 years. The researchers found that in men and women who watched >14 hours of television compared to <7 hours, the risk of metabolic syndrome was 2.07 and 1.48 times greater. Further, in those who were more (>2.5 hours per week) the risk of metabolic syndrome was 0.73 and 0.53 for men and women compared to less (<2.5 hours per week) active individuals.
Bertrais et al. The researchers examined the association between time spend in sedentary occupations, taking into account habitual physical activity and metabolic syndrome in 1,902 and 1,932 French men and women, 50 – 69 years of age. The researchers found that the risk of metabolic syndrome increased in line with the number of hours in front of a screen and decreased with increasing physical activity levels. Further, the researchers observed that the risk of metabolic syndrome reduced by one third and two thirds in participants meeting moderate and vigorous intensity physical activity guidelines respectively.
Chaput et al. The researchers examined the association between duration of sleep and metabolic syndrome in 810 participants of the Quebec family study. The researchers adjusted for confounding factors including age, sex socioeconomic factors, physical activity, nutrition and health behaviours. The researchers found that a U-shaped curve existed wherein 7 – 8 hours of sleep was associated with reduced risk of metabolic syndrome. The researchers found that subjects that slept for <6 hours were estimated to have a 76% greater risk of having metabolic syndrome.
Pan et al. The reviewers performed a meta-analysis to investigate the association between depression and metabolic syndrome among cross-sectional cohort studies. The reviewers found that an association exists between depression and metabolic syndrome.
Xi et al. The reviewers performed a meta-analysis to investigate the effect of sleep duration on the risk of metabolic syndrome including 12 cross-sectional cohort studies of 18,720 individuals with metabolic syndrome and 70,833 controls. The reviewers found that individuals who sleep for adequate durations (7 – 8 hours) are 27% less likely to develop metabolic syndrome than those that less sleep for <6 hours.
Park et al. The researchers examined the association between metabolic syndrome and lifestyle factors among South Korean adults aged 20 – 79 participating in the Korean National Health and Nutrition Examination Survey in 1998. The researchers found that the prevalence of metabolic syndrome was 14.2% and 17.7% in men and women, respectively. The researchers found that lifestyle factors including age, body mass index (BMI), and current smoking were positively associated with having the metabolic syndrome, but moderate exercise 2 – 3 days per week in men, and light alcohol consumption in women were found to be inversely associated with the metabolic syndrome.
Boonyavarakul et al. |The researchers examined the prevalence and associated risk factors of metabolic syndrome in a rural population of Thai adults aged >35 years." The researchers found that the prevalence of metabolic syndrome was similar to that in other countries (17%) and higher body mass index (BMI) and body fat percentage were significantly associated with an increased likelihood of metabolic syndrome.
Zhu et al. The researchers examined the data from the Third National Health and Nutrition Examination Survey conducted between 1988 – 1994 and assessed the association between metabolic syndrome and modifiable lifestyle factors. The researchers found that low physical activity, high carbohydrate intake in men, and current smoking habits were associated with an increased likelihood of metabolic syndrome.
Shin et al. The researchers investigated the association between dietary and eating habits and metabolic syndrome in Korean adults. The researchers found that metabolic syndrome increased with age and was significantly associated with higher intake of seaweed and oily foods, as well as more frequent overeating or eating more quickly.
Dhingra et al. The researchers investigated the prevalence of metabolic syndrome in middle-aged adults with different habitual intakes of soft drinks who were participating in the Framingham Heart Study. The researchers found that those individuals who consumed >1 soft drinks per day were at a greater risk of metabolic syndrome than those who consumed <1 per day.

Based on these studies, it appears that the main risk factors for developing metabolic syndrome are age and gender, being overweight and having high body fat percentage, elevated levels of inflammatory biomarkers such as C-reactive protein, low physical activity, greater time spent sedentary, smoking, lack of sleep, and depression.


Can exercise help treat metabolic syndrome?

Various researchers have assessed the effectiveness of exercise training for the treatment of metabolic syndrome, as follows:

Study Method Finding
Stewart et al. The researchers performed a randomised control trial of 115 adults aged 55 – 75 years to investigate the effect of 6 months of exercise training fitness and body composition. The researchers wanted to examine whether changes in either would affect the presence of metabolic syndrome. The researchers found that following the exercise intervention, aerobic fitness, lean mass, and HDL-C were all significantly increased, while total fat mass and abdominal fat body mass were significantly reduced. Further, the researchers reported that 42.3% of the participants had metabolic syndrome prior to the trial. Afterwards, they found that 17.7% of the exercisers and 15.1% of the controls no longer had metabolic syndrome, and 7.6% of the control group had developed it. The researchers also reported that the reductions in total and abdominal body fat were more strongly correlated with the risk factors of metabolic syndrome than the changes in fitness.
Dumortier et al. The researchers investigated the effect of 2 months of individual aerobic endurance training in participants with metabolic syndrome on insulin sensitivity and body composition. The endurance exercise intensity was individualised so that maximal relative lipid oxidation (‘fat burning’) would occur. The researchers found that participants lost significant amounts of fat mass (1.55kg), waist circumference (3.53cm) and hip circumference (2.2 cm). They reported that the changes in body composition were significantly associated with greater insulin sensitivity.
Irving et al. The researchers investigated the effect of exercise intensity on changes in abdominal and visceral fat, and body composition in 27 middle-age women with metabolic syndrome. The women performed a 16-week exercise training program. The subjects were randomly assigned to either: (1) no exercise, (2) maintaining current physical activity levels, (3) exercise performed under the lactate threshold 5-times-per week, or (4) exercise above the lactate threshold 3 times per week plus exercise below the lactate threshold 2 times per week. Caloric expenditure was adjusted to maintain 400 kcal per session for both groups 3 and 4. The researchers found that the high-intensity exercise program significantly reduced abdominal, subcutaneous and visceral abdominal fat following the intervention but no significant findings occurred in the other groups.
Tjønna et al. The researchers investigated the effect of (1) moderate continuous aerobic exercise, or (2) high intensity aerobic interval training of equal volume on variables associated with cardiovascular function, and existence of metabolic syndrome in 32 patients with metabolic syndrome. The researchers randomly allocated the subjects to either a control group or 3-times-weekly exercise sessions for 16 weeks. The exercise sessions comprised either continuous exercise (70% of heart-rate maximum) or aerobic interval training (90% heart-rate maximum). The researchers reported that aerobic interval training improved maximal oxygen consumption (VO2-max) significantly more than continuous exercise (35% vs. 16%). Further, the researchers reported that high-intensity interval training removed more metabolic syndrome risk factors (5.9 before vs. 4.0 afterwards) compared with continuous exercise (5.7 before vs. 5.0 afterwards). The researchers reported that interval training was superior in improving endothelial function (9% vs. 5%), as well as insulin signalling. Lastly, the researchers reported that both types of exercise were equally effective at reducing mean arterial blood pressure, bodyweight and fat mass.
Balducci et al. The researchers investigated the effect of either high-intensity aerobic exercise, or aerobic exercise + resistance-training matched for calorie expenditure, in comparison with a sedentary control group on inflammatory markers such as high sensitivity-C reactive protein (CRP). The exercise interventions lasted 12 months and measures were taken at baseline and every 3 months. The researchers reported that insulin sensitivity, HDL-C, waist circumference, albuminuria and peak oxygen consumption increased in both the aerobic exercise and aerobic exercise + resistance-training groups. The researchers reported that CRP reduced in both exercising groups. The researchers found that changes in CRP were strongly predicted by changes in peak oxygen consumption and the type of exercise performed, independent of changes in body weight. The researchers concluded that exercise modality and intensity have an independent association with improvements in inflammatory levels irrespective of induced weight loss.
Stensvold et al. The researchers investigated the effect of different training regimens (aerobic interval training, resistance-training, or a combination program) for the treatment of metabolic syndrome and the reduction of associated cardiovascular abnormalities in 43 subjects with metabolic syndrome. The subjects performed an exercise program 3 times a week for 12 weeks. The researchers reported that after the program, all 3 groups displayed significantly improved waist circumference and endothelial function, while peak oxygen consumption was improved following aerobic (11%) and combination training (10%) but not following resistance-training alone. They found that maximal strength was improved following resistance-training alone (45%) and combination training (31%) but not following aerobic interval training alone. They observed no changes in fasting blood glucose, HDL-C or bodyweight in any group.
Tjønna et al. The researchers investigated the effect of a single bout of exercise before and after a 16 week exercise program in twenty-eight patients with metabolic syndrome. The participants were randomly allocated to either an aerobic interval training group or to a continuous, moderate-intensity exercise program. The researchers measured flow mediated dilation before, immediately afterwards, and 24, 48 and 72 hours after a single bout of exercise, both pre- and post-intervention. The researchers found that the aerobic interval training group improved flow mediated dilation immediately post-exercise more so than the continuous exercise group.
Katzmarzyk et al. The researchers investigated the effect of a 20-week program of supervised aerobic exercise in 621 participants of the HERITAGE family study on the prevalence of metabolic risk factors in individuals who were identified as having metabolic syndrome. Of the 621 participants, 105 (16.9%) were diagnosed as having metabolic syndrome at the start of the exercise program. The researchers reported that following the program, 30.5% of these subjects were no longer classified as having metabolic syndrome. Of these 32 subjects, 43% of them displayed decreased triglyceride levels, 16% of them displayed improved HDL-C, 38% improved blood pressure, 9% improved fasting blood glucose and 28% reduced waist circumference.
Johnson et al. The researchers investigated the effect of exercise volume and intensity in improving the risk factors compromising the metabolic syndrome. The researchers randomly allocated 334 subjects to either a 6-month control group or one of three, 8-month exercise interventions. The interventions comprised (1) low volume/moderate-intensity exercise, (2) low volume/vigorous-intensity exercise, and (3) high volume/vigorous-intensity exercise, which were equivalent to 19, 19 and 32 km/week of walking and jogging, respectively. The researchers reported that both the low volume/moderate-intensity and high volume/vigorous-intensity exercise led to significantly greater reductions in risk factors compared to inactive controls. However, the researchers found that the low volume/vigorous-exercise did not display any significant differences from the inactive controls. Further, the high volume/high-intensity exercise group demonstrated significantly greater improvements in risk factors compared to all groups, which supports the idea of an exercise dose-response effect. The researchers conclude that even low amounts of exercise similar to the recommended guidelines of 30 minutes/day in the absence of dietary changes have beneficial effects on metabolic syndrome. However, they also concluded that a higher amount of vigorous-intensity exercise had greater and more widespread benefits.
Tibana et al. The researchers investigated the effect of 8 weeks of resistance-training on changes in anthropometric, cardiovascular and risk factors for metabolic syndrome in 14 overweight and obese middle-age women. The resistance-training program consisted of full body constant-load resistance-training for 3 sets of 8 – 12 repetitions, 3-times-per-week. The researchers found no significant changes in A1C, plasma glucose, HDL-C, triglycerides and anthropometric indices as a result of the training program.
Dallek et al. The researchers investigated the effect of a 14-week community-based exercise program aimed at reducing the risk factors of metabolic syndrome. The researchers retrospectively analysed the presence of metabolic syndrome components in 332 participants. The researchers found that following the 14-week program, all component risk factors except cholesterol were significantly reduced. They reported that the prevalence of participants with the metabolic syndrome reduced from 22.3% to 13.5% while the prevalence of participants without metabolic syndrome increased by 56%.
Strasser et al. The reviewers performed a systematic review and meta-analysis of 13 trials investigating the effect of resistance-training on risk factors of metabolic syndrome. The reviewers found that resistance-training demonstrated clinical and statistically significant metabolic risk factors, including as obesity, A1C levels and systolic blood pressure.
Lakka et al. The reviewers conducted a review of exercise for the treatment of metabolic syndrome. The reviewers reported that exercise has demonstrated a mild-to-moderately favourable effect on many of the risk factors and components of the metabolic syndrome. Further, they report that unstructured physical activity may also reduce the incidence of metabolic syndrome and must be considered as an effective way to protect against it. The reviewers report that brisk walking is a feasible and accessible exercise modality and current recommendations of 30 minutes daily can be recommended as the principal form of exercise for this population. Additionally, if contraindications allow, more vigorous forms of exercise may be considered to obtain additional health benefits.
Castenada et al. The researchers investigated the effect of 16 weeks of progressive resistance training (3 days per week) on changes in metabolic syndrome risk factors and measures of glucose control. The researchers found that following the resistance-training program, there were significant reductions in systolic blood pressure and abdominal fat, suggesting that resistance-training has beneficial effects on the metabolic abnormalities associated with metabolic syndrome.
Levinger et al. The researchers investigated the effect of resistance-training on the activities of daily living (ADLs) and quality of life in 55 individuals aged 50.8 years, with both high and low numbers of metabolic risk factors. The researchers found that total fat body mass and peak oxygen consumption increased in the group with a low number of metabolic risk factors, while a significant increase in quality of life was reported in the group with a high number of metabolic risk factors. Moreover, the researchers found that strength increased following the intervention in both groups, and time to complete ADLs improved by 8.8% and 9.7% in the low and high number groups, respectively.
Ha et al. The researchers investigated the effect of a 12-week exercise program consisting of both aerobic exercise and resistance-training. The program comprised 80-minute bouts, 3 times per week, including a warm-up, cool-down and 30 minutes of both aerobic (at 60 – 80% heart-rate maximum) and resistance-training (10 – 15RM) in 16 female college students. The researchers found that the exercise program did not result in changes in triglycerides, total, LDL-C or HDL-C and fasting glucose. However, the researchers observed significant improvements in body fat percentage, waist circumference, systolic blood pressure and diastolic blood pressure.
Nuri et al. The researchers investigated the effect of exercise training on the changes of the risk factors associated with the metabolic syndrome in 29 postmenopausal women aged 58 years, with breast cancer. The researchers randomly allocated the subjects to either a control or exercise group. The exercise group performed 15 weeks of both aerobic exercise and resistance-training, including 2 days of walking exercise and 2 days of resistance exercise. The researchers found that following the exercise program, significant improvements occurred in peak oxygen consumption, systolic blood pressure, waist-to-hip ratio, fasting insulin and glucose, HDL-C and triglycerides. The researchers concluded that a combination exercise training program can positively affect postmenopausal women with breast cancer.
Lee et al. The researchers investigated the effect of 16 weeks of yoga exercise on changes in metabolic syndrome risk factors in 16 obese postmenopausal Korean women with >36% body fat, aged 54 years. The researchers randomly allocated the subjects to either a yoga group or to a control group. The researchers found body composition, LDL-C, triglycerides, total cholesterol, blood pressure, plasma insulin and glucose all decreased significantly in the yoga group, while HDL-C and adiponectin both increased.
Bateman et al. The researchers investigated the effects of an 8-month aerobic exercise, resistance-training or combination exercise program on the effects of metabolic syndrome in 144 participants. Of those, 86 participants were retrospectively reported to have a complete set of criteria for the metabolic syndrome at baseline. The researchers randomly allocated the participants to one of three groups: (1) resistance-training, 3 days per week (including 3 sets of 8 – 12 repetitions of 8 exercises), (2) aerobic exercise consisting of 120 minutes per week at 75% peak oxygen uptake), and (3) a combination of these programs. The researchers found that following the exercise intervention, resistance-training alone displayed no effect on metabolic risk factors, while aerobic exercise alone displayed a non-significant trend towards improvements in metabolic risk factors. However, the researchers found that the combination program significantly improved the metabolic risk factors.
Huang et al. The researchers performed a systematic review and meta-analysis to investigate the effect of aerobic interval training in comparison with moderate-intensity, continuous aerobic exercise on changes in aerobic capacity and metabolic risk factors in individuals with cardio-metabolic disorders. The researchers reviewed 6 randomized control trials including 153 participants during energy expenditure-matched exercise programs. The reviewers reported that aerobic interval training significantly improved peak oxygen consumption to a greater extent than moderate-intensity continuous aerobic exercise, and displayed a trend towards greater reductions in fasting blood glucose. However, the researchers report that changes in metabolic risk factors were not different between interval and continuous exercise programs.
Lima et al. The researchers investigated the effect of aerobic training on changes in blood press in menopausal women with metabolic syndrome. The researchers recruited 44 women and randomly allocated them to one of four groups: )1) menopausal control, (2) non-menopausal control, (3) menopausal aerobics and (4) non-menopausal aerobics. The researchers reported that all groups reduced abdominal fat, reduced blood glucose and improved peak oxygen consumption. Compared to pre-intervention, no group demonstrated changes in systolic or diastolic blood pressure. The researchers reported that exercise program improved metabolic syndrome components but did not alter resting blood pressure among middle-age women with and without menopause.

Based on these studies and reviews, it appears that both aerobic (including various types of aerobic training) and resistance exercise are useful for improving specific risk factors and reducing the prevalence of metabolic syndrome.


Can combined exercise and lifestyle interventions help treat metabolic syndrome?

Various researchers have assessed the effectiveness of exercise training for the treatment of metabolic syndrome, as follows:

Study Method Finding
Anderssen et al. The researchers investigated the single and combined effect of diet and exercise on the prevalence of metabolic syndrome after 1 year of the intervention in 136 men aged 40 – 49 years. The researchers randomly allocated the subjects to 4 groups: (1) diet intervention, (2) exercise intervention, (3) diet and exercise intervention, and (4) control. Following the 1 year intervention, the researchers measured the prevalence of metabolic syndrome among the men as classified by the International Diabetes Federation. The researchers found that among the intervention groups, the number of men still having metabolic syndrome were 32.6%, 64.7%, 76.5% in the diet + exercise, diet alone, and exercise alone groups. The researchers concluded that both exercise and diet interventions reduced the prevalence of metabolic syndrome, the combination of diet and exercise was significantly greater than either intervention alone.
Okura et al. The researchers investigated the effect of aerobic exercise in women with metabolic syndrome in response to a weight loss intervention. The researchers randomly allocated the 67 overweight and obese women to either a 14 week diet intervention to induce weight-loss, or the same weight-loss diet with the addition of aerobic exercise. The researchers found that the risk of metabolic syndrome was reduced following diet alone (1-fold reduction) and even more reduced following diet and exercise (3.6-fold reduction). The researchers report that adding exercise to a weight-loss diet significantly enhances the reduction in risk of metabolic syndrome.
Bo et al. The researchers investigated the effect of a 12-month intervention of general lifestyle recommendations (reduced saturated fats, increased fiber/polyunsaturated fats and exercise) compared to a control group receiving standard unstructured information on the prevalence of metabolic syndrome among 375 adults aged 45 – 64 years. The researchers found that waist circumference, C-reactive protein, HDL cholesterol and bodyweight were significantly reduced following the lifestyle intervention, whereas these components increased in the control group. The researchers reported that the lifestyle intervention significantly reduced the prevalence of metabolic syndrome, with an absolute risk reduction of 31%.
Johnson et al. The researchers investigated the effect of exercise volume and intensity in improving the risk factors compromising the metabolic syndrome. The researchers randomly allocated 334 subjects to either a 6-month control group or one of three, 8-month exercise interventions. The interventions comprised (1) low volume/moderate-intensity exercise, (2) low volume/vigorous-intensity exercise, and (3) high volume/vigorous-intensity exercise, which were equivalent to 19, 19 and 32 km/week of walking and jogging, respectively. The researchers reported that both the low volume/moderate-intensity and high volume/vigorous-intensity exercise led to significantly greater reductions in risk factors compared to inactive controls. However, the researchers found that the low volume/vigorous-exercise did not display any significant differences from the inactive controls. Further, the high volume/high-intensity exercise group demonstrated significantly greater improvements in risk factors compared to all groups, which supports the idea of an exercise dose-response effect. The researchers conclude that even low amounts of exercise similar to the recommended guidelines of 30 minutes/day in the absence of dietary changes have beneficial effects on metabolic syndrome. However, they also concluded that a higher amount of vigorous-intensity exercise had greater and more widespread benefits.
Potteiger et al. The researchers investigated the effect of 6 months of either resistance-training or aerobic exercise, combined with an energy-restricted diet on changes in the risk factors of metabolic syndrome in 24 male adults between 27 – 48 years with >1 risk factor of metabolic syndrome. The exercise interventions were matched for frequency and duration of sessions and were progressed over 3 months until each group were performing exercise 4 days per week for 45 minute bouts. The researchers found that following the 6 month intervention, the aerobic training group significantly reduced measured by a calculated metabolic syndrome z-score but resistance-training only displayed a non-significant reduction. The researchers concluded that both aerobic exercise and resistance-training in conjunction with energy restriction improve the risk factors of metabolic syndrome.
Dutheil et al. The researchers investigated the effect of various volumes of exercise with a combination of resistance-training and aerobic exercise in conjunction with an energy-restricted diet on changes in abdominal visceral fat, risk factors of metabolic syndrome and body composition, Framingham score and cardiovascular function. The subjects randomly allocated 100 subjects, aged 50 – 70 years to (1) moderate resistance/moderate aerobic, (2) high resistance/moderate aerobic, or (3) moderate resistance/high aerobic groups. The subjects performed a 21-day residential program followed by a 1-year home-based program. The researchers found that abdominal visceral fat loss was greatest in the high resistance group (-18%) than in the other groups. They reported that improvements were generally greater in the high-intensity groups compared to the moderate-intensity groups. Further, the researchers report that the components of metabolic syndrome improved in all groups by was not significant between groups. However, changes in the components of metabolic syndrome correlated with reductions in abdominal visceral fat.
Meckling et al. The researchers investigated the effect of a modified energy restricted diet containing either a 1:1 or 3:1 ratio of protein-to-carbohydrates with or without the addition of a combination (resistance and aerobic) exercise program in 44 overweight and obese women. The intervention groups were designated as (1) control diet (1:1 protein-to-carbohydrate) with exercise, (2) high protein without exercise, and (3) high-protein with exercise. The intervention lasted 12 weeks and pre- and post- measures of weight, blood lipids, blood pressure, plasma insulin levels, body composition, nitrogen balance, fitness, and resting energy expenditure were taken. The researchers found that weight-loss was greatest in the high-protein with exercise group (7.0kg) compared to all other groups. The researchers reported that all groups significantly improved body composition, blood pressure and waist-hip circumference. Further, blood lipids were improved following the control diet with exercise and high protein without exercise group, decreased triglycerides in the high protein with exercise and LDL-C decreased in the high protein group only. The researchers report that dietary changes with exercise demonstrate significant benefits on some of the components of the risk factors for metabolic syndrome.

Based on these studies and reviews, it appears that exercise as part of a lifestyle intervention improves changes in body composition and risk factors, and reduced the prevalence of metabolic syndrome in population based studies.


Conclusions

On the basis of these studies and review, the following conclusions might be drawn:

Area Conclusion
Metabolic syndrome is increasingly common and increases with age and ethnicity Prevalence of metabolic syndrome can range from 4.2% – 49.8% depending on the population studied. Older populations tend to display greater prevalence of metabolic syndrome than younger populations, as do non-white Caucasian adults compared to white and European adults.
Risk factors for metabolic syndrome The main risk factors for developing metabolic syndrome are age and gender, being overweight and having high body fat percentage, elevated levels of inflammatory biomarkers such as C-reactive protein, low physical activity, greater time spent sedentary, smoking, lack of sleep, and depression.
Exercise is beneficial for metabolic syndrome Both aerobic exercise (including various types of aerobic training) and resistance-training appear to be useful in improving specific risk factors and reducing the prevalence of metabolic syndrome.
Exercise in combination with lifestyle interventions Exercise as part of a lifestyle intervention seems to improve body composition and metabolic syndrome risk factors, and reduces the prevalence of metabolic syndrome in population based studies.

In summary, metabolic syndrome is increasingly common and increases with age and ethnicity. The main risk factors include age and gender, being overweight and having high body fat percentage, elevated levels of inflammatory biomarkers such as C-reactive protein, low physical activity, greater time spent sedentary, smoking, lack of sleep, and depression. However, exercise is beneficial for the treatment and prevention of metabolic syndrome.


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