In a recent study funded by the National Institutes of Health, obesity researchers from the University of Michigan have found that physical exercise is effective in suppressing appetite.

Which would be amazing, except there’s one little catch. 

The study, presented at The Endocrine Society‘s 90th Annual Meeting in San Francisco looked at the association between:

  • exercise,
  • leptin (a hormone linked to appetite),
  • and obesity.

In the study, the researchers took at a group of post-menopausal women (a group prone to increased central adiposity aka belly fat due to the shift in hormones) and put them on a treadmill for morning and afternoon workouts. The women performed either a high intensity workout or a more traditional lower intensity cardio workout.

Throughout the day, each participant was asked to rank their level of hunger based on a scale of 1 to 10. Numerous blood samples were also taken to measure their level of leptin.

At the end of the study, the blood tests revealed that while the obese women in the group had much higher levels of leptin in their blood, they did not report any appetite suppression during exercise.

So what’s the catch?

  • In normal weight individuals, an increase in leptin results in a decrease in appetite.
  • However, in overweight individuals, the same increase in leptin has little effect on appetite due to a lower sensitivity to leptin – the same sort of problem type 2 diabetics have with insulin. As a result, even though more and more leptin is produced, the overweight person’s resistance to leptin throws their appetite out of whack.
  • For the lean women in the study, both types of workout reduced their levels of leptin. And a reduced level of leptin should result in an increase in appetite.


However, while I seem to be pooping all over this study, I did find something very interesting. And that was, during the exercise, the lean women felt no increase in hunger even as their leptin levels were dropping.

Unfortunately, the information that the Endocrine Society released about this study did not mention the appetite of the lean women post-workout. Something that would have been very interesting to learn.

For the overweight women in the study, the high intensity workout had no effect on the level of leptin. However, the moderate, cardio type workout did cause leptin to fall.

So what do we take from this?

  1. Being overweight messes up your appetite control system. No surprise here.
  2. The researchers in this study were hoping to see an obvious connection between leptin, exercise, appetite and obesity. This didn’t happen. Appetite control and obesity is verrrryyyyy complex and it seems the more we know about it’s influences the more confusing it gets.
  3. Overweight individuals can NOT trust their appetite if they want to lose their excess body-fat.
  4. More research needs to be done on this subject.
  5. It’s pretty cool how the human body works.