Does Slow Reintroduction of Calories After Weight Loss Prevent Weight Regain in Trained Athletes? A Feasibility Study

Rationale:

About 66% of the adults in the United States are overweight or obese [Ogden 2006]. Multiple factors are likely to be involved in the development of this epidemic, including increased dietary fat and caloric intake, as well as decreased levels of physical activity. Public health efforts have emphasized the role of preventing weight gain as a means of preventing the complications of obesity such as a number of adverse medical conditions [Allison 1999], lower quality of life [Kolotkin 2001] and reduced life expectancy [Allison 1999]. Obesity is the result of a long term condition of positive energy balance. Energy expenditure is on the output side of the equation while food intake or caloric intake is on the input side of the equation.

Total Daily Energy Expenditure (TDEE) exists of three components, Resting Energy Expenditure (REE), the minimum amount of energy spent to maintain bodily functions, which on average is responsible for 60-70% of TDEE, the Thermic Effect of Food (TEF), the energy necessary for the absorption and digestion of the food we eat, which takes up about 10%, and Physical Activity related energy expenditure, which varies largely from day to day depending on the amount of activity performed [de Jonge 1997]. This includes Non-Exercise Activity Thermogenesis (NEAT), the energy expenditure from fidgeting or moving (Levine, 2004). A low REE has been shown to be a predictor of weight gain over time [Ravussin 1993]. It is well known that weight loss results in a decrease of REE, due in part to a decrease in lean body mass, the strongest predictor of REE [Tataranni 1995], but also due to a metabolic adaptation to the caloric restriction, resulting in a higher energy efficiency which serves to prevent further weight loss and conserve energy. However, this energy conservation is also responsible for the weight regain after weight loss [Martin 2007]. Many obesity treatments are therefore focused on limiting the decrease in REE as much as possible whether is by diet, exercise, medication or a combination of the three in order to slow down the process of weight regain. The applicant's research program has focused on the prevention of weight regain and metabolic adaptation to changes in diet and energy balance over the past 20 years.

Physique and powerlifting athletes often submit themselves to periods of caloric restriction in the weeks before a competition or a meet in order to reach their desired leanness or weight category. In the period shortly after cessation of the restrictive diet body mass will quickly return to pre-diet values with a disproportionate gain of fat mass. To avoid this rapid fat gain 'reverse dieting' has become popular among athletes. This involves slowly increasing caloric intake in a slow, stepwise fashion. The theory behind this is that the small increase in caloric intake might help to restore energy expenditure toward pre-dieting levels and decrease the chance of increasing fat mass. While anecdotal reports of successful reverse dieting have led to an increase in popularity, research is needed to evaluate its true efficacy. In addition, only reports in trained athletes are available at this moment while, if the method would work in non-athlete individuals, this could be an important change in the risk of weight regain after a weight loss diet. However, since this method has been used in the weight training population, the proposed study will use this population to test the feasibility and fine tune the measurement schedule.

The aim of the proposed project is therefore twofold: