How your appetite will change

Peta resting after a session.

One of the main reasons I find Fast Exercise helps with weight control is that, unlike many other fitness approaches, it stems my appetite rather than increases it. When I have trained for marathons, putting in hour upon hour of lengthy runs, my overwhelming response is to eat like a horse. There is no doubt exercise burns calories, but at the kind of level most of us work out, it also stimulates hunger. The more moderate activity we do, the more we eat, effectively cancelling out the weight loss benefits.

It is what scientists refer to as ‘compensation’ eating. And studies have shown that moderate exercise typically increases the production of so-called ‘hunger hormone’ ghrelin. The more moderate activity we do, the more we eat, effectively cancelling out the weight loss benefits. In other words, workouts of this kind can work up your appetite.

Where Fast Exercise differs is in its ability to suppress appetite.

After a shorter, more intense workout, however, I finish feeling as if I couldn’t face food.

Why is this? Human appetite is complicated and influenced by everything from environment cues and brain signals to genes and mood. But emerging evidence seems to confirm that the more effort we put into exercising, the better the outcomes in terms of calories consumed afterwards.

One study at the University of Wyoming found that ghrelin levels did indeed spike after a group of women ran at a decent speed, but that the vigorous exercise also caused a rise in levels of other hormones, including one called peptide YY, that prompt feelings of satiety. Invited to eat as much as they liked at a buffet, the runners chose to consume several hundred calories less than they had consumed after not having done exercise. Blood tests seemed to confirm that the rise in satiety hormones “muted” the hunger message from ghrelin. Notably, when the tests were repeated on women who walked or sat down, the results were entirely different. The moderate walking didn’t cause augmented blood levels of the satiety hormones and, as a result, the walkers overate at the post-workout buffet.

And the more intense the exercise, the longer the appetite benefits seems to last. There are theories that the body needs to circulate more blood to prevent overheating when you push yourself hard. Because eating would cause blood to flow to the stomach instead to aid digestion, your body temporarily dampens your appetite to prevent that reaction. Consistency is also crucial.

The more often you exercise, the more in tune you become with your hunger signals which may help to offset them.

Norwegian scientists found that after a 12 week exercise program, subjects began recognizing, without consciously knowing it, that they should not consume too many calories when they finished. Fast exercise, in particular, appears to help restore sensitivity to brain neurons that control satiety.