Post-workout cravings: how to control your ravenous hunger after exercise
Intense workouts can curb your appetite in a similar way to weight-loss jabs. Here, experts reveal what to do, and when, to keep you from post-gym snacking.
If a workout makes you feel so hungry that you overeat when you finish, you might question its value, at least in terms of it helping with weight loss. Select the right sort of exercise, however, and your appetite could be curbed enough to make a positive difference on the scales.
Researchers intrigued by the relationship between exercise and hunger levels have even found that putting more effort into a workout might have similar effects to drugs such as semaglutide, marketed as Wegovy, the weight-loss jab.
“One of the mechanisms by which intense exercise suppresses appetite could relate to GLP-1, the hormone that is the basis for some of these drug treatments for obesity,” says David Stensel, professor of exercise metabolism at Loughborough University. Semaglutide works by mimicking GLP-1 (glucagon-like peptide-1), which makes you feel full by slowing down stomach emptying and suppressing appetite. You eat less because you don’t feel ravenous. Stensel says his own and other research has found that vigorous activity elevates levels of GLP-1 “so there are indeed similarities in the mechanism behind the anti-obesity drugs that potentiates the hormone, although at a much reduced level”.
This autumn, Stensel and his team will be embarking on a study that will use functional MRI equipment to scan the brains of people to see how they respond to weight-loss drugs such as Wegovy. “Within that there could be an exercise component to assess their physical activity levels and what happens to exercise habits when people take this sort of medication,” he says. “We believe exercise has a role to supplement these drugs and might potentially help to lower the dose required or to maintain longer-term weight loss.”
That is the tip of the iceberg in this field of research, he says, yet there are many other biological mechanisms that are known to play a role in appetite control when people pick up the pace of their exercise. “There’s a wide-held belief that people who do gentle exercise such as walking are more likely to reward themselves after finishing and therefore offset any calories they have worked off,” Stensel says. “We haven’t found that in any of our lab-based studies, and light activity doesn’t seem to have an effect and neither increases nor reduces hunger, but what is clear is that intense exercise leads to suppression of appetite.”
One key player is ghrelin, a hormone that stimulates appetite, and which is known to be dampened down by a bout of sweaty exercise. “Studies have shown that when animals are infused with ghrelin they eat more,” Stensel says. “So, in theory, if you can suppress it in humans, they will eat less.” A downside is that effects are relatively short-lived. Within 30 to 60 minutes of finishing a workout, ghrelin levels return to near normal.
“Levels of GLP-1 and another satiety hormone called peptide YY, which is also released from the small intestine, can remain elevated for several hours after a single bout of exercise,” says Dr Alice Thackray, a senior research associate in exercise metabolism who works alongside Stensel at Loughborough. “In terms of the longer-term effects, we haven’t yet looked at whether these hormones remain raised for 24 hours or longer, but if you exercise the next day and perform repeated exercise bouts, then appetite could be affected longer-term.”
Researchers at Wilfrid Laurier University in Canada are also looking at the effects on hunger levels of lactate, a waste product produced by muscles during intense exercise. In one recent study published in the Journal of Applied Physiology they compared high-intensity interval training (HIIT) on a bike or treadmill with 20 minutes of running at a gentle pace. Blood tests revealed that lactate levels were predictably high in the HIIT exercisers, and the higher the lactate level, the lower the level of ghrelin, suggesting a potent appetite-suppressing effect.
Indeed, in food diaries completed during the 24 hours after the lab-based workouts, the high lactate HIIT group reported consuming up to 201 fewer calories than the moderate-paced runners, a small but potentially significant reduction if repeated several times a week. “Whether lactate is involved is a new theory being studied in terms of effect appetite,” Stensel says. “It is one of the mechanisms gaining attention.”
Healthy habits remain important. Stensel says that most studies have looked at immediate post-exercise effects on hunger and not much is yet known about whether those effects persist longer-term. That means repeated bouts of regular exercise are important for continuing appetite suppression. And it goes without saying that the post-workout snack should be avoided. “Popping into a coffee shop after a workout for a smoothie or protein bar just replaces the calories you have expended in a workout and will undo any gains if you are pursuing weight loss,” Stensel says. “Unless you are an athlete you do not need to refuel after exercise.” Here’s what else you can try to stem hunger pangs:
1. Add intervals to your exercise
In the Wilfrid Laurier University study, researchers compared the effects of an easy run with two different HIIT-style workouts: one entailing 60 seconds of all-out running on a treadmill followed by 60 seconds of gentle jogging or walking, repeated ten times; the other comprising eight 15-second sprints on an indoor bike with two minutes of rest between each burst. A control group sat and relaxed. Lactate levels were much higher after the two HIIT workouts and participants ate 129 fewer calories after the running HIIT and 201 fewer calories after the bike session compared with the controls. The steady-state running, meanwhile, had no effect on appetite and food intake. “Generally studies show that the more effort you make with exercise, the better the effect on your appetite,” Stensel says. “However, HIIT isn’t for everyone and the all-out effort required certainly doesn’t favour people who are not very fit to start with, so my advice would be to add bursts of pushing hard relative to your own fitness level when and where you can.”
2. Work out earlier in the day
David Clayton, a senior lecturer and researcher in nutrition and exercise physiology at Nottingham Trent University, recently discovered that a mid-morning workout might be more beneficial when it comes to stemming hunger than exercise performed later in the day. Participants in his trial were asked to eat a standardised meal of a tuna or chicken sandwich, crisps and a chocolate bar the night before each workout. The next day they ate a standardised breakfast of porridge, a cereal bar and yoghurt at 8.30am before completing a 30-minute steady-state cycle on an indoor bike followed by a “performance test” in which they were asked to cycle as hard and far as possible within 15 minutes at 10.30am. They repeated this exercise assessment at 6.30pm on a different day, having consumed the same breakfast and standardised meals two hours before their workout. “We then asked them to rate their feelings on hunger and fullness on a scale,” Clayton says. “And we also asked them to detail how much food they ate at a meal 15 minutes post-workout.” Results showed that, while performance didn’t change, participants ate more after evening workouts and less in the morning.
3. Choose cycling over swimming
As tempting as it might be to take a dip when it’s warm outside, swimming is likely to leave you hungrier than before you dived in. Anecdotally, swimming makes you hungry (I certainly find it does for me), so in an earlier study the Loughborough team including Thackray and Stensel put that theory to the test. They recruited healthy young adults and asked them to complete an hour of swimming or cycling, each performed as intervals of eight minutes’ hard effort and two minutes’ active rest, on different days, and then invited them to eat as much as they liked at a carb-laden buffet half an hour after they finished working out. A control group sat down for an hour before attending the buffet. Results showed that hunger spiked after swimming, with participants consuming an average 142 calories more than the control group. After cycling, they also ate more than after sitting, but only 94 extra calories, considered to be not significantly different to the effects of resting. According to the researchers, the body uses more energy to generate heat when submerged in cool water, which might be one reason for post-pool cravings.
4. Go for a run or a walk
Good news, you don’t have to go eyeballs out with sprints and intervals to get healthy and curb appetite. “Adding a bit more effort to a walk or run will be enough to burn more calories and properly to reduce appetite to some degree,” Thackray says. In one of her studies, she asked people to do a 60-minute bout of fairly vigorous but consistent running - no intervals involved - at about 70 per cent of their maximum pace. Subjects reported feeling less hungry and more full after the exercise compared to a control group. Even an hour of moderate walking could be enough to prevent overeating. “Regardless of whether it’s gentle or vigorous, exercise will have a lesser or greater impact on calorie expenditure and consumption,” Stensel says. “If you are doing it daily, it will potentially help with weight control.”
