It is time to bust the myth of physical inactivity and obesity: you cannot outrun a bad diet
A Malhotra, T Noakes, S Phinney
British Journal of Sports Medecine Published Online First 22 April 2015
A recent report from the UK's Academy of Medical Royal Colleges described ‘the miracle cure’ of performing 30 min of moderate exercise, five times a week, as more powerful than many drugs administered for chronic disease prevention and management.1 Regular physical activity reduces the risk of developing cardiovascular disease, type 2 diabetes, dementia and some cancers by at least 30%. However, physical activity does not promote weight loss.
In the past 30 years, as obesity has rocketed, there has been little change in physical activity levels in the Western population.2 This places the blame for our expanding waist lines directly on the type and amount of calories consumed. However, the obesity epidemic represents only the tip of a much larger iceberg of the adverse health consequences of poor diet. According to the Lancet global burden of disease reports, poor diet now generates more disease than physical inactivity, alcohol and smoking combined. Up to 40% of those with a normal body mass index will harbour metabolic abnormalities typically associated with obesity, which include hypertension, dyslipidaemia, non-alcoholic fatty liver disease and cardiovascular disease.3 However, this is little appreciated by scientists, doctors, media writers and policymakers, despite the extensive scientific literature on the vulnerability of all ages and all sizes to lifestyle-related diseases.
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And what about carbohydrate loading for exercise?
The twin rationales for carbohydrate loading are that the body has a limited capacity to store carbohydrates and these are essential for more intense exercise. However, recent studies suggest otherwise. The work of Volek and colleagues8 establishes that chronic adaptation to a high-fat low-carbohydrate diet induces very high rates of fat oxidation during exercise (up to 1.5 g/min)—sufficient for most exercisers in most forms of exercise—without the need for added carbohydrate. Thus fat, including ketone bodies, appears to be the ideal fuel for most exercise—it is abundant, does not need replacement or supplementation during exercise, and can fuel the forms of exercise in which most participate.8 If a high-carbohydrate diet was merely unnecessary for exercise it would be of little threat to public health, however, there are growing concerns that insulin-resistant athletes may be at risk of developing type 2 diabetes if they continue to eat very high-carbohydrate diets for decades since such diets worsen insulin resistance.
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It is time to wind back the harms caused by the junk food industry's Public Relations machinery. Let us bust the myth of physical inactivity and obesity. You cannot outrun a bad diet.
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