The Role of Diet and Exercise for the Maintenance of Fat-Free Mass and Resting Metabolic Rate During Weight Loss

Abstract

The incidence of obesity is increasing rapidly. Research efforts for effective treatment strategies still focus on diet and exercise programmes, the individual components of which have been investigated in intervention trials in order to determine the most effective recommendations for sustained changes in bodyweight. The foremost objective of a weight-loss trial has to be the reduction in body fat leading to a decrease in risk factors for metabolic syndrome. However, a concomitant decline in lean tissue can frequently be observed. Given that fat-free mass (FFM) represents a key determinant of the magnitude of resting metabolic rate (RMR), it follows that a decrease in lean tissue could hinder the progress of weight loss. Therefore, with respect to long-term effectiveness of weight-loss programmes, the loss of fat mass while maintaining FFM and RMR seems desirable. Diet intervention studies suggest spontaneous losses in bodyweight following low-fat diets, and current data on a reduction of the carbohydrate-to-protein ratio of the diet show promising outcomes. Exercise training is associated with an increase in energy expenditure, thus promoting changes in body composition and bodyweight while keeping dietary intake constant. The advantages of strength training may have greater implications than initially proposed with respect to decreasing percentage body fat and sustaining FFM. Research to date suggests that the addition of exercise programmes to dietary restriction can promote more favourable changes in body composition than diet or physical activity on its own. Moreover, recent research indicates that the macronutrient content of the energy-restricted diet may influence body compositional alterations following exercise regimens. Protein emerges as an important factor for the maintenance of or increase in FFM induced by exercise training. Changes in RMR can only partly be accounted for by alterations in respiring tissues, and other yet-undefined mechanisms have to be explored. These outcomes provide the scientific rationale to justify further randomised intervention trials on the synergies between diet and exercise approaches to yield favourable modifications in body composition.

Physical Activity and Abnormal Blood Glucose Among Healthy Weight Adults

“…[31][32][33] Muscle strength, decreases in visceral adiposity, and improved insulin sensitivity have all been associated with higher levels of physical activity. 34,35 Future studies should investigate diabetes risk, exercise, lean muscle mass, and visceral adiposity in healthy weight individuals.…”

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.…”

An isoenergetic high-protein, moderate-fat diet does not compromise strength and fatigue during resistance exercise in women

“…The need to implement studies on high-protein diets and physical activity has been stressed recently (15) . The effects of a 7 d high-protein diet on endurance performance have been investigated by Jarvis et al (6) and Macdermid & Stannard (7) , who reported ergolytic effects on cycling endurance performance in recreational and highly trained athletes, respectively.…”