Cardio, fat loss and evidence Although we do not discount the numerous benefits of regular endurance exercise on various aspects of health (e.g. improving lipid profiles and insulin sensitivity), we do think it is time to reconsider how we promote exercise as a means of inducing fat loss. Indeed, the plethora of studies that demonstrate that exercise produces less than an expected weight loss appears consistent with our conclusion that in non-fasted individuals, exercise has little effect on daily fat oxidation. We offer that in individuals performing moderate amounts of exercise (e.g. < 1 hr/day), the primary benefit of endurance exercise on body weight may be in preventing additional weight gain or in preventing weight regain after weight loss, but understanding exactly how to prescribe exercise to achieve fat mass loss requires further investigation. Finally, we suggest that it is time to put the myth that low-intensity exercise promotes a greater “fat burn” to rest. Clearly, exercise intensity does not have an effect on daily fat balance, if intake is unchanged. We must educate the public that participation in moderate doses of exercise will not burn more fat unless changes are made to energy or fat intake. Ref.: Melanson EL, MacLean PS, Hill JO. Exercise improves fat metabolism in muscle but does not increase 24-h fat oxidation. Exerc Sport Sci Rev. 2009 Apr;37(2):93-101. doi: 10.1097/JES.0b013e31819c2f0b. Fourteen trials were included, but only 12 trials involving 910 women contributed data to outcome analysis. Women who exercised did not lose significantly more weight than women in the usual care group (two trials; n = 53; MD -0.10 kg; 95% confidence interval (CI) -1.90 to 1.71). Women who took part in a diet (one trial; n = 45; MD -1.70 kg; 95% CI -2.08 to -1.32), or diet plus exercise programme (seven trials; n = 573; MD -1.93 kg; 95% CI -2.96 to -0.89; random-effects, T² = 1.09, I² = 71%), lost significantly more weight than women in the usual care group. There was no difference in the magnitude of weight loss between diet alone and diet plus exercise group (one trial; n = 43; MD 0.30 kg; 95% CI -0.06 to 0.66). The interventions seemed not to affect breastfeeding performance adversely Ref:. Amorim Adegboye AR, Linne YM. Diet or exercise, or both, for weight reduction in women after childbirth. Cochrane Database Syst Rev. 2013 Jul 23;7:CD005627. doi: 10.1002/14651858.CD005627.pub3. Weight loss resulting from an exercise intervention tends to be lower than predicted. Modest weight loss can arise from an increase in energy intake, physiological reductions in resting energy expenditure, an increase in lean tissue or a decrease in non-exercise activity. Lower than expected, weight loss could also arise from weak and invalidated assumptions within predictive models. To investigate these causes, we systematically reviewed studies that monitored compliance to exercise prescriptions and measured exercise-induced change in body composition. Changed body energy stores were calculated to determine the deficit between total daily energy intake and energy expenditures. This information combined with available measurements was used to critically evaluate explanations for low exercise-induced weight loss. We conclude that the small magnitude of weight loss observed from the majority of evaluated exercise interventions is primarily due to low doses of prescribed exercise energy expenditures compounded by a concomitant increase in caloric intake. Ref.: Thomas DM, Bouchard C, Church T, Slentz C, Kraus WE, Redman LM, Martin CK, Silva AM, Vossen M, Westerterp K, Heymsfield SB. Why do individuals not lose more weight from an exercise intervention at a defined dose? An energy balance analysis. Obes Rev. 2012 Oct;13(10):835-47. doi: 10.1111/j.1467-789X.2012.01012.x. Epub 2012 Jun 11. Body weight, anthropometric, and body composition changes were evaluated at 12 months and are presented in Table 2. Participants in the diet alone group lost a mean 7.2 kg (−8.5%, P
Posted on: Fri, 15 Aug 2014 20:24:29 +0000
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