What is the Relationship Between Exercise and Metabolic Abnormalities?

Abstract

Prevention of the metabolic syndrome and treatment of its main characteristics are now considered of utmost importance in order to combat the epidemic of type 2 diabetes mellitus and to reduce the increased risk of cardiovascular disease and all-cause mortality. Insulin resistance/hyperinsulinaemia are consistently linked with a clustering of multiple clinical and subclinical metabolic risk factors. It is now widely recognised that obesity (especially abdominal fat accumulation), hyperglycaemia, dyslipidaemia and hypertension are common metabolic traits that, concurrently, constitute the distinctive insulin resistance or metabolic syndrome. Cross-sectional and prospective data provide an emerging picture of associations of both physical activity habits and cardiorespiratory fitness with the metabolic syndrome. The metabolic syndrome, is a disorder that requires aggressive multi-factorial intervention. Recent treatment guidelines have emphasised the clinical utility of diagnosis and an important treatment role for 'therapeutic lifestyle change', incorporating moderate physical activity. Several previous narrative reviews have considered exercise training as an effective treatment for insulin resistance and other components of the syndrome. However, the evidence cited has been less consistent for exercise training effects on several metabolic syndrome variables, unless combined with appropriate dietary modifications to achieve weight loss. Recently published randomised controlled trial data concerning the effects of exercise training on separate metabolic syndrome traits are evaluated within this review. Novel systematic review and meta-analysis evidence is presented indicating that supervised, long-term, moderate to moderately vigorous intensity exercise training, in the absence of therapeutic weight loss, improves the dyslipidaemic profile by raising high density lipoprotein-cholesterol and lowering triglycerides in overweight and obese adults with characteristics of the metabolic syndrome. Lifestyle interventions, including exercise and dietary-induced weight loss may improve insulin resistance and glucose tolerance in obesity states and are highly effective in preventing or delaying the onset of type 2 diabetes in individuals with impaired glucose regulation. Randomised controlled trial evidence also indicates that exercise training decreases blood pressure in overweight/obese individuals with high normal blood pressure and hypertension. These evidence-based findings continue to support recommendations that supervised or partially supervised exercise training is an important initial adjunctive step in the treatment of individuals with the metabolic syndrome. Exercise training should be considered an essential part of 'therapeutic lifestyle change' and may concurrently improve insulin resistance and the entire cluster of metabolic risk factors.

Metabolic and behavioral responses to high-fat feeding in mice selectively bred for high wheel-running activity

“…A high fat content in the diet increases weight gain and the risk of developing symptoms of the 'metabolic syndrome' in a number of species, including human beings 2,24 and various rodents. [3][4][5][6] This study investigated whether and how such an effect may be influenced by physical activity.…”

“…When these metabolic abnormalities are displayed in concert (often referred to as the 'metabolic syndrome'), they have a high risk of developing into life-threatening conditions such as cardiovascular disease and diabetes mellitus type 2 (for review, see Moller and Kaufman 1 ). Consensus exists that increased dietary fat intake in combination with a sedentary lifestyle are precipitating factors (World Health Organization), 2 but the underlying endocrine and metabolic mechanisms are poorly understood.…”

“…15 Given that adiponectin is known to facilitate triglyceride breakdown, [20][21][22] it might be hypothesized that these animals are resistant to HFD-induced obesityFover and above the effects of increased energy expenditure caused by elevated spontaneous activity. Thus, in this study, female and male mice from a line bred for high spontaneous wheel-running activity and from a nonselected control line were exposed to an HFD with two main objectives: (1) to test the hypothesis that a trait for high spontaneous physical activity can cause resistance to obesity and other indicators of the metabolic syndrome (2) and to investigate the potential behavioral, endocrine and metabolic mechanisms underlying this resistance.…”

Is weight loss the optimal target for obesity-related cardiovascular disease risk reduction?

“…For example, three months of daily aerobic training in obese men, who consumed compensatory kilocalories equivalent to the amount expended during exercise, resulted in a 30% improvement in insulin sensitivity despite no change in weight (14). Furthermore, while improvements in HDL cholesterol and TGs are generally greater in those who lose weight, these improvements can be seen even when weight remains virtually unchanged (49)(50)(51). For example, a number of physical activity interventions that do not significantly alter body weight have documented 5% to 35% reductions in TG levels (52,53) and/or 3% to 5% increases in HDL values (32,52).…”

Regular physical exercise in patients with type II diabetes mellitus

“…It is believed to control hyperglycemia through the improvement of peripheral insulin sensitivity particularly in skeletal muscle [22,38]. In addition, many studies have also described exercise as a countermeasure against many abnormalities observed in diabetic patients, such as hyperlipidemia, hypertension, and a tendency for hypercoagulation [7,10,47], which are considered to increase the risk of macro-and microvascular complications [21,46]. These and many other chronic complications of diabetes mellitus seem to be attenuated by the regular practice of physical exercise.…”