Have you ever started a new exercise routine, only to find yourself constantly hungry? Have you ever finished a hard morning workout and been surprised by your lack of appetite that day? The effect our workouts have on our appetite has long been a source of fascination, not only for athletes and sportsmen, but also for scientists.
Recently, a study published in the journal Nature shed some additional light on the possible links between how we exercise and how we eat. And interestingly, it all goes back to a single molecule.
Meet the New “Anti-Hunger” Hormone
Conducted by a group of scientists from Stanford Medicine, Baylor University, and the University of Copenhagen, this multiphase study showed that at least some of the effects of exercise on appetite involve a single molecule, which is a mixture of lactate and phenylalanine. Appropriately named lac-phe by the researchers, this molecule increased in the blood of mice after exercise more than any other molecule tested.
This came as a surprise to the researchers, as much of the previous research on appetite has focused on leptin and ghrelin, the two main hormones that control hunger signals. Ghrelin, which is produced when the stomach is empty, signals the brain that it’s time to eat; Leptin, which is produced in the small intestine and suppresses your appetite, lets your brain know when you’re full. But lac-phe quickly became a source of interest for the researchers, who continued the study by testing how lac-phe affects the animals’ appetite on its own.
To do this, they fed lac-phe to obese mice and saw their food intake drop by more than 30 percent. Finally, the researchers bred mice into two groups: the first group could produce lac-phe and the second could not. They had both groups of mice perform intense workouts, in this case running on a treadmill, for several weeks, and observed their eating habits. The results clearly showed that the mice that could not produce lac-phe in response to their training ate significantly more food and gained 25 percent more weight than the mice that could produce the molecule.
The results showed that this molecule, which scientists now refer to as the “anti-hunger” hormone, made the difference between overeating after a workout and not.
Related: What is the best time of day to exercise?
Intense workouts for appetite control
Knowing how lac-phe affects appetite is one thing, but how can we as humans take advantage of this new knowledge? Fortunately, the group of researchers also explored the role of lac-phe in humans, analyzing the blood of eight young men before and after three different types of exercise: leisurely cycling, lifting weights, and then running on a stationary bike. The results showed that men’s blood lac-phe levels increased more after sprints and less after prolonged, leisurely cycling, suggesting that intense workouts may produce more lac-phe and surprise appetite. , better than the slower ones. physical activity.
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If you’ve noticed that you lose your appetite on the day of an intense workout, lac-phe might explain why. And according to Kevin Libby, nutritionist and founder of PH2 Nutrition, this is something fitness and nutrition professionals have been looking at for years. “If you’re training for something that requires a lot of resistance or intensity, that type of exercise can be interpreted as a perceived threat to your body,” explains Kevin Libby. “Cuts down your appetite to help you escape the threat,” he continues. According to Libby, long training sessions, like an athlete training for something, “can make food sound like the worst thing in the world.”
That said, he also points out that certain workouts can also increase your appetite. For example, “after a HIIT workout, your appetite can skyrocket, especially for carbohydrates like rice, potatoes, and pasta,” he explains. Why? “During a HIIT workout, you’re consuming a ton of oxygen and you’re burning all your glucose and glycogen, so your body really wants to replace all of that post-workout,” says Libby.
According to Libby, even though this study gives us a better idea of how fitness affects our appetite. As he explains: “This also depends a lot on the person. Not everyone’s appetite will react the same way to exercise.”
Related: Don’t have time to exercise? Why ‘snacking with exercise’ could be an easy fix
How to avoid post-workout cravings
If you find yourself feeling hungry after a workout or starting a workout routine, “That’s totally normal to a degree,” says Libby. That’s because you’re burning calories when you exercise and if you’re not eating enough to replace those calories, you’ll start to break down muscle. “You need to give yourself the right energy to increase performance,” she explains.
This study suggests that adding more intestinal forms of exercise, such as boxing, long-distance running, or an intense spin class, might help control the appetite response. If she’s battling post-workout hunger, Libby also recommends focusing on avoiding high-calorie, low-nutrient foods like processed foods or fast food. She’s going to have a ton of unhealthy fats and refined processed carbs.
Instead, “Have a good post-workout meal that’s low on the glycemic index,” says Libby. That means protein, healthy fats, and slow-burning carbs like sweet potatoes, squash, and brown rice. Another option is to do your workout later in the day instead of first thing in the morning. “This can help curb your appetite, since you have a few meals and your body isn’t fasting,” says Libby.
Next: New Research Says Intense Exercise Can Curb Cravings – Start With These 4 Exercises
- Kevin Libby, nutritionist and founder of PH2 Nutrition
- Li, VL, He, Y., Contrepois, K. et al. An exercise-inducible metabolite that suppresses eating and obesity. Nature 606, 785–790 (2022). https://doi.org/10.1038/s41586-022-04828-5