Many exercisers report weight control or weight loss as one of their main goals for performing a weekly exercise program. While exercise can produce a caloric deficit, especially when combined with a nutritional caloric deficit, our bodies have significant physiological mechanisms to avoid weight loss. For example, many participants will create a caloric deficit through diet and exercise, but the body can increase our appetites or reduce our overall energy expenditure on other activities to balance this initial deficit. In our Boulder Physical Therapy practice, many report an increase in appetite after some exercise programs as the body looks to replace, and sometimes over consume, burned calories from exercise. An interesting new research finding demonstrates why we may feel hungry or disinterested in replacing these burned calories after exercise.
Li and colleagues in the journal Nature published their findings on a new metabolite produced during exercise that may be responsible for controlling hunger after workouts (2022). Authors conducted both animal and human exercise trials and have found a new metabolite in our blood stream (Lac-Phe) which is increased after bouts of energy expenditure. Increases in Lac-Phe, either through drug supplementation or natural production, reduces appetite while absence of Lac-Phe causes participants to increase food intake after exercise bouts. Authors have found the highest levels of Lac-Phe with intense aerobic exercise and less with strength training, but the lowest levels were found with low intensity exercise. This metabolite likely explains the appetite suppression found with higher intensity exercise that can help participants control hunger while beginning an exercise program.