THE problem with exercise as a weight loss strategy is many of us use it as a way justify an extra slice of pizza or another glass of wine.
But as it turns out, how hungry you are post workout depends on how intense or how long that workout really was.
A recent study published in Journal of Endocrinology recruited 16 healthy, fit young men (sorry, no women due to controlling for the effects of women’s menstrual cycles). Participants were split into two groups: One group focused on intensity, ranging from an easy jog for 55 minutes (50% of their maximum capacity) to a more vigorous pace for 36 minutes (75% of maximum capacity), until they burned around 600 calories.
The second group focused on length with a run for 45 minutes at a steady pace on one day, followed by a run for 90 minutes at the same pace on another day (70% of maximum capacity). Throughout the experiment, both groups ate standard meals and levels of ghrelin — a hormone thought to influence appetite was measured. Generally speaking, when ghrelin levels rise, so does hunger.
Results reveal that our appetites certainly are strange, influenced by many factors beyond hormones and burning calories. In general, exercise lowered ghrelin (making people less hungry) with the effects being more pronounced when runs were vigorous (above 75% maximum capacity) and longer (90 minutes) compared to gentler jogging or briefer runs (45 minutes).
Interestingly, hormones remained suppressed one-hour post workout when workouts were the longest. What’s more, those who ran for 90 minutes reported feeling less hungry compared to those who carried out short, intense workouts, who soon felt peckish, despite still having low levels of ghrelin in their blood.
WHAT DOES THIS MEAN?
Granted the study was small and did not follow up whether participants had replaced the calories they had burned post workout, but this study shows that some types of exercise may be better than others at blunting appetite and potentially aiding in weight management. That is, you may wish to increase the duration of each session if you want to whittle the waistline.
WHY YOU’RE HUNGRY AFTER A WORKOUT
It’s true that we’re not all the same when it comes to weight loss and there are individual differences in the effect exercise has on appetite. Despite it boiling down to the type of workout you’re doing (intense vs. low-intensity sessions), studies show that the level of fitness also impacts appetite.
In other words, the less fit you are, the more famished you’ll be. That’s because your body and brain haven’t gotten used to your workout habit yet, suggesting that a regular exercise habit might help us to regulate our appetites better.
Another reason is dehydration. Many times our bodies mistake thirst for hunger, so if you’re not drinking enough water throughout your workout, hunger may be intensified.
Let’s remember exercise has many other benefits irrespective of weight loss: elevated mood, immune boosting, reduced blood pressure, and improved fitness, to name a few.
Current Australian physical activity guidelines recommend 150-300 minutes of “moderate” intensity physical activity or 75-150 minutes of “vigorous” activity a week.
Australians are nowhere near active enough, and for someone trying to keep their weight in check, guidelines recommend adults increase to 300 minutes (five hours) or 60 minutes of moderate intensity activity on most days of the week.
Kathleen Alleaume is an exercise and nutrition scientist and author of What’s Eating You?