Many of us have experienced the frustration of losing weight, only to see the pounds creep back on. This "rebound weight gain" is common, no matter how you lose weight—whether through diet, exercise, weight loss drugs, or even surgery. But why does this happen, and what can we do about it?
Understanding Rebound Weight Gain
Our bodies are surprisingly stubborn when it comes to weight loss. When we diet, our body thinks we're in danger of starving and tries to "protect" us by:
- Increasing our appetite
- Slowing down our metabolism
- Storing fat more efficiently
These changes can last long after we've stopped dieting, making it easy to regain weight.
Recent weight loss drugs like semaglutide (Wegovy/Ozempic) and tirzepatide (Mounjaro/Zepbound) have shown great results. However, when people stop taking these medications, they often regain about half the weight they lost within a year, even with continued lifestyle changes like watching their diet and exercising. People who had no lifestyle interventions after stopping semaglutide gained back over two-thirds of what the medication helped them lose.
So Why Is It So Hard to Keep Weight Off?
There’s been a lot of research into why rebound weight gain occurs, and it’s still ongoing. What is certain, is that it’s much more complex than ‘poor willpower’. Here are some reasons:
Energy Gap: When we eat less, we have reduced nutrients available to our body and lowered energy stores, leading to reduction in hormones like leptin and insulin. This signals certain areas in our brain to burn fewer calories and make us hungrier, the so-called “energy gap”. If we don’t actively try to ignore these energy gap signals, we’re likely to overeat until the lost weight is regained (and even exceeded). Basically, our brains are trying to sabotage the weight loss through hormones, not through poor willpower!
Body Fat Memory: Our body seems to remember its previous weight and tries to return to it. Certain immune cells in various tissues and organs seem to play a role in this and actively promote the release of substances from our cells that impair our glucose metabolism and insulin sensitivity. Fat is stored in our bodies as brown or white fat. Whereas brown fat cells burn energy to produce heat, can help regulate sugar and fat metabolism and help you burn calories (so it’s a good kind of fat), white fat is not your friend. It’s the most common type of fat in our bodies, stores energy (rather than burns it), and is the site of long-term inflammation in the overweight and obese—activating the immune cells mentioned above.
Brain Changes: Weight gain may cause lasting inflammatory changes in the part of our brain that controls appetite and is associated with increased fat around our organs, insulin resistance, glucose intolerance, diabetes and (more) weight gain. That sounds like a vicious cycle!
Gut Bacteria: The balance of bacteria in our gut (our “gut microbiome”) changes with weight loss and gain, which might affect our weight. For example, in obesity the microbiome is less diverse, and the gut can become ‘leaky’, both of which are triggers for inflammation (which is not good: see Body Fat Memory above). In fact, it’s been discovered that obese adults had a reduction in a particular gut bacteria that was then linked to the brain changes mentioned earlier and an uptick in eating fats. In animal studies, it’s been shown that the less healthy microbiome in obese mice persisted after they lost weight and likely led to faster rebound weight gain.
Fat Cells: Health adults have a relatively constant number of fat cells (‘adipocytes’) as new ones are created and old ones are cleared out. However, the size of our fat cells varies within pockets of fatty tissue. When we lose weight, our fat cells shrink but don't disappear. However, they’re ready to store fat again if given the chance! Changes in adipocyte volume with weight loss may stress the fat cells and contribute to a biological drive to regain weight. What’s more, animal studies showed that early in the relapse process (after weight loss), the adipocytes didn’t just expand but actually increased in number too—and then continued to grow in size. Even worse, this increase in the number of adipocytes seems to be a permanent effect. It’s thought that some of us with a genetic tendency for obesity gain back more weight than we originally lost because of this increase in both the number and size of our fat cells.
Changes in fat cells with weight loss and weight regain
Adapted from MacLean et al. Obesity Reviews. 2015;16 (Suppl 1):45-54. doi: https://doi.org/10.1111/obr.12255
What About Those New Weight Loss Drugs?
Medications like semaglutide and tirzepatide work by mimicking a hormone in our body called GLP-1, which helps control appetite and blood sugar. These drugs are very effective, but—much like those for high blood pressure or diabetes—they only work as long as you keep taking them. Many people stop using them due to side effects, cost, or because they've reached their goal weight. This applies to people taking them for diabetes as well as weight loss. In fact, in one study, half of patients with diabetes stopped taking GLP-1 mimics and were more likely to stop these diabetic medications than other types.
With GLP-1 mimics there may be another factor at play in weight regain too. In addition to the various things our bodies do to regain weight, there’s a theory that these mimics suppress our natural production of GLP-1. So, when we stop the medication, we have a ‘double whammy’ effect: we’ve stopped taking the substance that has been making us feel full and slowing our stomach emptying (both of which suppress our appetite), but we’ve also dampened down our own production of this helpful hormone. Add those effects to the body’s attempt to regain weight and it’s no wonder that people have rebound weight gain after stopping these “skinny shots”!
A Possible Solution: Activating Our Body's Natural GLP-1
Researchers in New Zealand have found a natural substance from hops that can boost our body's own production of GLP-1. This patented extract, called Amarasate®, is the active ingredient in an all-natural supplement called Calocurb®. It’s been studied for over 14 years in New Zealand in multiple clinical trials (in humans, not mice!). For example, when we eat, GLP-1 naturally rises so that our body gets a message to stop eating. When Amarasate was taken an hour before a meal, it doubled the natural peak in GLP-1 that occurs with eating, and the participants ate almost 20% fewer calories at the subsequent meal. When taken during a 24-hour water fast, women’s hunger was reduced by 30% overall and men’s hunger by 25%. It’s been available in New Zealand for over 6 years, with reports of people losing up to 60 pounds (almost 30 kg). In fact, there’s a new study being done in New Zealand right now that will measure weight loss in overweight and obese people who take Calocurb for six months.
Side effects with Amarasate are rare, but because up to 10% of people may get diarrhea when starting it, in most cases it should be started slowly and the dose gradually built up.
Amarasate might be useful in two ways for people who are or have been taking GLP-1 mimics like semaglutide and tirzepatide:
- Taken along with these weight loss drugs to help maintain the body's natural GLP-1 production. In fact, some weight loss doctors have reported that if they start their patients on Amarasate at the same time as they start the skinny shots, they’ve been able to use lower doses of the medication, and their patients had fewer side effects.
- Used when stopping weight loss drugs to help the body kick start itself into making more GLP-1 on its own. For this, weight loss doctors advise starting Amarasate in the same week that the last dose of the medication is taken. People who transition to Amarasate from the medications don’t need to start the supplement as slowly as usually suggested.
If you’re thinking of starting GLP-1 mimics or have been on them but want to stop them, ask your weight loss doctor about using Amarasate either when you start the skinny shots or when you’re stopping them.
The Bottom Line
Losing weight is hard but keeping it off can be even harder. Our bodies have many ways of trying to regain lost weight. While new medications can help, they need to be taken long-term to maintain weight loss. Natural supplements like Amarasate might offer a more affordable way to help keep weight off in the long run. Remember, maintaining a healthy weight is a lifelong journey, not a quick fix.
- Written for Calocurb by Dr. Tracey Lambert
