Latest Briefing in Food, health and wellbeing for 2010

The role of muscle in appetite control

Diet and lifestyle change are likely to be the most pragmatic approaches to reducing obesity and improving outcomes for co-morbidities such as diabetes. Dieting is often the primary approach to weight loss, however, dieting in most cases is ineffective over the long term, with lost weight regained when dieting ceases. This is due to a combination of a reduced metabolic rate experienced during weight loss and the action of a powerful homeostatic system in the brain to defend a perceived appropriate body mass. Exercise is a lifestyle change that is often tried alone or in conjunction with diet to reduce weight and has beneficial effects on metabolic health in addition to weight loss, including improvement in insulin sensitivity. Exercise combined with dieting is often the most effective intervention at weight loss maintenance.

Depending upon the level of exercise, food intake may or may not be adjusted to compensate for energy expended. In humans the relationship between exercise and food intake seems poorly connected at least over short timescales and in the longer term energy expenditure may be compensated for by increased food intake in some individuals and not in others.

Skeletal muscle is the largest pool of protein in the body and constitutes nearly 50% of total body mass, contributing up to 40% of energy expended in the resting state. During growth protein is required to provide the building blocks of increased muscle mass. Studies in juvenile rodents at RINH have shown that during growth when lean mass (muscle) is increasing, protein content of a diet determines the level of food intake.  This would implicate lean mass as an important determinant of food intake and suggests that food intake is set by the requirement to satisfy the need to maintain or increase lean tissue. This is important as lean mass varies as a result of obesity, dieting and exercise as well as lifestage, increasing dramatically in early years during growth and decreasing in later life, leading to sarcopenia (loss of muscle) in the elderly.

Recently the discovery of the cytokine, IL-6 as a circulating hormone produced and secreted from contracting muscle supports the contention that hormones produced and secreted from muscle can influence metabolism and establishes muscle as an endocrine organ. This discovery provides a conceptual basis for communication between exercised muscle and organs of the body including the brain. Until now we have not appreciated the potential influence of muscle on the ability to regulate appetite and that muscle derived factors produced during exercise, growth or in response to nutrient availability could relay a signal either directly or indirectly to the brain to adjust feeling of hunger and behaviour, including amount or type of food consumed for short-term and long-term needs.

Published on 10 December 2010 in Food, health and wellbeing

Briefings in Food, health and wellbeing for 2010