Hormones Drive Weight Regain After Dieting

A study in the New England Journal of Medicine shows that rebound weight gain isn’t just a matter of having no willpower. Hormones play a huge role.

Let me explain.

Hormones related to appetite and hunger can be disrupted by dieting and weight loss, and can remain so for at least one year. When these hormones are out of whack, you can experience tremendous hunger and cravings, and even the best intentions can easily be derailed.

“Maintaining weight loss may be more difficult than losing weight”, said lead researcher Joseph Proietto, PhD, a professor of medicine at the University of Melbourne’s Heidelberg Repatriation Hospital, in Victoria, Australia. “This may be due to biological changes rather than [a] voluntary return to old habits”.

I’ve said for decades that weight loss is relatively easy—it’s keeping it off that’s the issue for most people. (I’m always reminded of my father’s quip about stopping smoking: “It’s easy to stop smoking”, he’d always say, “I myself have done it 20 times!”)

Researchers have long known that hormones found in the pancreas (like insulin and glucagon), the gut and the fatty tissues have a huge influence on body weight not to mention hunger, appetite and calorie burning. And when body fat percentage drops, that causes a decrease in certain hormones like leptin  while at the same time causing an increase in hormones like ghrelin.

Leptin- when working properly– puts the brakes on eating by sending a signal to the brain saying, “Hey! Stomach’s full! Stop shoveling the food in!”. Ghrelin, on the other hand, does the exact opposite, effectively telling the brain, “Don’t listen to leptin! This dude’s starving! Chow down!”

A decrease in the stop signals (leptin) coupled with an increase in the go signals (ghrelin) is a prescription for disaster when it comes to weight gain.

The hormone changes that happen during weight loss have been known to scientists for ages. But what wasn’t clear before this new study was how long the hormonal changes actually persist.

In the study, Proietto and his research team put 50 overweight men and women on a very low-calorie diet for ten weeks and then monitored their hormone levels for a full year.

During the initial period on the low-cal diet, the average weight loss was 30 pounds, representing about 10% of starting body weight for most of the participants. Blood tests confirmed that levels of the hormones that affect appetite and weight gain (insulin, ghrelin and leptin) had indeed changed as expected. And- not surprisingly—the participants also reported being hungrier.

After ten weeks on the low-calorie weight loss diet, the participants were told they could resume a “normal” diet, but they were given periodic advice by a dietitian and also strongly encouraged to get a half-hour of exercise on most days of the week. After a year, most of the participants had regained an average of 12 pounds.

But the blood tests showed that hormone levels hadn’t really stabilized fully. And hunger levels remained a bit elevated as well.

The moral of this story isn’t that you have to be a victim of your hormones. But it does mean that there are some hidden forces driving appetite and the more you can get them under control the better prepared you are. One of these “powerful forces” is the hormone insulin (also known—for good reason— as the “fat storage hormone”).

Another of these forces—not discussed in the present study—is brain chemistry. In my weight loss program, New You in 22, we spend a great deal of time addressing the brain chemistry of cravings and appetite, and teaching you how to reprogram your brain so that these cravings don’t rule your life and determine your behavior. Sure, you may still feel a little stirring when you smell a Cinnabon baking, but you won’t be as compelled to do something about it!

A healthy respect for hormones and brain chemistry is always a good thing, but it’s also good to remember that there’s a lot in our power that can affect these things, and that their power over us can be strongly modified by the actions we take and the choices we make.


Ask questions

Take A Free Assessment!

Want to know more about how your hormones affect you?  My friend Glen Depke has made his Adrenal Assessment available to the  Jonny Bowden community for free. You can access it by clicking here.





  1. Valerie H

    I don’t think this is the whole story. I read Why We Get Fat and What Do Do About It by Gary Taubes. The idea I took away from that book is that fat storage is controlled by insulin. There is something in metabolically damaged people which causes fat storage. I think the key to maintenance is switching the complex system that controls this.

  2. Slim5555


    Could you please address the effects of hormone changes in a woman post menopause ?
    Thank you, Slim

  3. Carmen Z.

    I can see why the participants in the study you cited regained 12 pounds. It’s hard to ignore hunger signals; if Ghrelin is telling your brain, “Go eat more” when you’re starving and Leptin is supposed to be signaling your brain to “stop” when you’re full but the whole system is out of whack, it makes total sense.…Here’s a little more info on resetting leptin. Fat cells are very metabolically active. They release and receive a variety of different hormones like leptin. The more body fat one carries, the more leptin that person has and vice-versa. The leaner someone is, the less leptin he or she will have. While it’s easier for an obese person to peel off the pounds faster, leaner individuals have a hard time burning off the last few pounds. A study done by Guerra, et.al. 2011 pointed out that to “reset” leptin levels one must exercise in a “fasted” state. Researchers found that a single sprint training session had powerful effects on leptin “signaling” in the fasted group. What if the participants were told to exercise for 30 minutes in a fasted state. Would that have made a difference?