Many people work out aggressively in order to maintain healthy body weight while still eating the things they enjoy. Of course, some self-control is needed here in order to not over eat as many people feel that a reward for an effective and aggressive workout should be a big meal. But what if an intense work out made you less likely to eat?
In a new study, 17 overweight men volunteered to participate in four exercise sessions. In the first, they rested, and in the subsequent three sessions, they cycled on stationary bikes at moderate, high, or very high intensity for 30 minutes.
After each of the exercise sessions, the men drank a 267-calorie liquid meal replacement. And, 70 minutes later, the men were asked to eat oatmeal, offered by researchers, until they were comfortably full.
The results were contrary to popular belief.
The men ate the least oatmeal after the very intense exercise. They ate 764 calories of oatmeal after resting, 710 calories after the moderate exercise, 621 calories after the high intensity workout and, most notably, 594 calories after the very high-intensity workout. Similar trends were seen in analyses of their calorie intake the entire day after particular work outs. They ate 2,000 calories over the day following the very high intensity workout, around 2,300 calories during the day after the moderate exercise, and more than 2,600 during the day following the resting session.
When blood samples were compared after each workout, information about appetite suppression was revealed.
It is important to note that this change in appetite is short-term. After completing a very high-intensity workout, the men had lower active ghrelin, higher blood lactate, and higher blood glucose compared to other workouts, including the resting session. Ghrelin is a hunger-stimulating protein in the body. It is produced by the small and large intestines to get us to increase our food intake to maintain a proper balance of nutrients in the body. It essentially prevents us from starving by making us feel hungry. When ghrelin levels are low, it means the body has enough energy, and we do not need to put more energy, or food, in.
When blood glucose is high, as it was after the very high-intensity workout, appetite tends to be suppressed because the body has enough energy to sustain itself and does not signal hunger.
High lactate levels in the blood are common after intense exercise. Lactate in the blood is indicative of muscle fatigue and a lack of oxygen. This is not problematic at lower levels; it merely means that the lactate, a byproduct of working muscles, is being utilized for energy instead of oxygen as there is little oxygen in the blood because the exercise has become so intense that oxygen cannot get to the muscles fast enough to be utilized. Higher levels, as those seen in this study, indicate that much energy is being used by the body’s cells as a result of the high-intensity exercise done. Extremely high levels are harmful, but those were not seen among the men in this study.
The overall results from the blood work on the men indicate that the very high-intensity exercise utilizes much energy already stored in the body. Similarly, it causes the body to not need to take in much energy in the form of food, as the body is already using its energy and has control mechanisms to prevent overeating, especially after working out.
This suppression of appetite may be used for more than just weight loss. It could be a potential therapy for those who are obese and overweight. A vigorous workout can unlock their stored energy to suppress appetite, helping these people maintain a healthy weight by curbing their appetite and using their body’s energy productively.
Source: Sim AY, Wallman KE, Fairchild TJ, Guelfi KJ. High intensity intermittent exercise attenuates ad-libitum energy intake. International Journal of Obesity. 2013.