Strength Training and Postexercise Metabolism Exercise and Postmeal Lipids Body Mass and Diabetes
Schuenke, M.D., Mikat, R.P., & McBride, J.M. 2002. Effect of an acute period of resistance exercise on excess postexercise oxygen consumption: Implications for body mass management. European Journal of Applied Physiology, 86, 411.
Background. Studies have shown that metabolism remains elevated for hours following resistance exercise, but no trials have gone beyond 16 hours (h) or followed a whole-body, high-intensity exercise protocol.
Study. To examine the duration of excess postexercise oxygen consumption (EPOC) following heavy resistance exercise, researchers at Ohio University studied seven healthy men (mean age, 22 years; mean percent body fat, 10.4 percent) engaged in a 31-minute period of resistance exercise. The program consisted of four circuits of bench presses, power cleans and squats. During sets, each subject used his own predetermined 10-repetition maximum and continued until failure. Oxygen consumption measurements were obtained at consistent times (34 h pre-, 29 h pre-, 24 h pre-, 10 h pre-, 5 h pre-, immediately post-, 14 h post-, 19 h post-, 24 h post-, 38 h post-, 43 h post- and 48 h postexercise). Postexercise measurements were compared to baseline measurements made at the same time of day.
Results. EPOC was significantly elevated (p < 0.05) above baseline values immediately post-, 14 h post-, 19 h post- and 38 h postexercise. Mean daily values for both postexercise days were also significantly elevated above the mean value for the baseline day.
Researchers’ Conclusions. These results suggest that EPOC duration following resistance exercise extends well beyond the previously reported duration of 16 h. The duration and magnitude of EPOC observed in this study indicates the importance of future research to examine a possible role for high-intensity resistance training in weight management for various populations.
Comments. It has yet to be determined how the EPOC induced by four circuits of heavy resistance exercise relates to actual weight and fat loss. Clearly, research has shown that fat-free mass increases with volumes of resistance exercise similar to and even smaller than the volume used in this study. How this magnitude of resistance training influences total body fat, visceral body fat (especially the abdominal stores, which are very closely related to diabetes and coronary disease) and the more atherogenic blood lipids (e.g., very low density lipoproteins, LDL cholesterol particle size and concentration) remains to be seen.
Pettit, D.S., & Cureton, K.J. 2003. Effects of prior exercise on postprandial lipemia: A quantitative review. Metabolism, 52, (4) 418-24.
Study. Exercise physiologists at the University of Georgia at Athens synthesized the results from studies examining the effect of exercise on postprandial lipemia (triglyceride [TG] response to a meal) to summarize the existing data and provide direction for future research.
Results. The researchers retrieved 38 effects from 555 people in 29 studies. The mean effect from all the studies was moderate; it indicated that people who performed exercise before meal ingestion exhibited a 0.5 standard deviation reduction (15 to 40 percent TG reduction) in the postprandial TG response relative to persons in comparison groups.
Study design, gender, age, type of meal ingested, exercise intensity, exercise duration and timing of exercise had no significant effect on the postprandial response (p > 0.05). There was, however, significant variation in effect size (magnitude of the responses)—for women for exercise performed within 24 hours of meal ingestion, and for exercise performed more than 24 hours before meal ingestion (p < 0.01).
In studies that reported the energy expenditure of exercise, there was a significant relationship between postprandial TG response and energy expenditure (r = -0.62, p = 0.02).
Researchers’ Conclusions. Results from this quantitative review of the literature suggest that exercise has a moderate effect on the postprandial lipemic response. The amount of energy expended during prior exercise may play a role in the magnitude of this effect. Other factors that may affect the response remain to be clarified.
Comments. The postprandial lipemic response is significant for several reasons. A prolonged and excessive postmeal TG response is associated with cardiovascular disease, diabetes and the metabolic syndrome. High and prolonged levels of TGs following a fatty meal expose the arterial wall to atherogenic particles (known to accelerate atherosclerosis) and decrease arterial function. Exercise that is regular and of sufficient quantity (energy expenditure ≥ 400 kilocalories) helps reduce the TG response to a meal by 15 to 40 percent.
It is also important to note that although exercise can help reduce the arterial lipid (TG) burden of a fatty meal, it does not justify the regular consumption of high-fat meals.
Burke, J.P., et al. 2003. A population perspective on diabetes prevention. Diabetes Care, 26, 1999-2004.
Study. Endocrinologists from the Mayo Clinic and the University of Texas at San Antonio evaluated the influence of obesity and prevention of weight gain on the incidence of type 2 diabetes. Subjects were participants in the San Antonio Heart Study, a prospective population-based study of Mexican Americans and non-Hispanic whites residing in San Antonio, Texas.
Burke and colleagues stratified body mass index (BMI) into four categories: normal (< 25), overweight (≥ 25 and < 30), obese (≥ 30 and < 35) and very obese (≥ 35). (BMI = body weight in kilograms divided by the square of height in meters.) The researchers then estimated the number and proportion of incident cases prevented by targeting each BMI category. In addition, they calculated the decrease in risk of developing type 2 diabetes associated with weight gain prevention across both the BMI and age spectra.
Results. Preventing normal individuals from becoming overweight would result in the greatest reductions in the incidence of type 2 diabetes. This step would lead to a 62 percent drop among Mexican Americans and a 74 percent drop among non-Hispanic whites. Preventing the entire population from gaining, on average, 1 BMI unit would result in reductions in the incidence of type 2 diabetes of 12.4 and 13.0 percent in Mexican Americans and non-Hispanic whites, respectively. The majority of cases of type 2 diabetes were in individuals who were overweight or mildly obese with a family history of type 2 diabetes.
Researchers’ Conclusion. To prevent the maximum number of cases of type 2 diabetes, public health resources should be directed toward preventing weight gain among normal and overweight individuals.
Comments. Especially for Mexican Americans, these are among the first data to show the efficacy of reducing BMI by single units. Obesity is a strong risk factor for the development of type 2 diabetes in multiple ethnic groups and remains a prime target of therapy. From the standpoint of medical and social cost savings, diabetes prevention is perhaps the most productive work that fitness professionals can engage in. In the last 3 years, more than 100 clinical trials and scientific reviews have justified adopting an exercise, dietary and weight management approach to those with prediabetes or the metabolic syndrome.