Have you ever lost weight on a diet only to gain it all back once the diet ends? If so, you’re not alone. Regaining lost weight, also known as weight-cycling or the yo-yo diet effect, is a common occurrence for 75% of people who diet.
Consider what happened to the Season 8 contestants of the popular television show, The Biggest Loser. You know that reality show, right? The one where over-weight contestants compete to see who can lose the most weight. Researchers decided to keep track of 14 contestants from the 2009 season and found that all but one person regained weight after six years.
Apparently, the metabolic rates of the contestants dropped as they shed the pounds and when they returned home after show, the weight came back, thanks to lower metabolic rates.
Let’s face it, many of us either struggle with weight loss and/or know and love people who do. Most overweight people know how hard it is to lose excess pounds and when they can’t maintain a healthy weight, they blame themselves. And just in case they don’t, we have a $35 Billion a year fad-diet industry to remind them otherwise. That’s unfortunate because science has repeatedly shown that the body works against dieters by modifying metabolic rates and hormone levels to pull them back to their original weights.
For millions of people struggling with weight gain, it’s a myth to think that will-power and the latest fad diet will ever provide a solution. To solve the obesity problem in the U.S., we need to stop listening to cultural myths and begin looking to science for real answers.
A recent scientific study shows that the gut microbiota plays a major role in weight regain after dieting.
Researchers at the Weizmann Institute of Science used laboratory mice to investigate the underlying mechanisms of weight-cycling. They hypothesized that changes in the gut microbiota (i.e., the trillions of microorganisms that populate the gut) plays a pivotal role in accelerated weight gain following diet.
To test their hypothesis, they exposed laboratory mice to a high-fat diet to induce obesity and then provided normal, vegetarian chow to cause weight loss. They repeated this process to cause weight-cycling (i.e., repeated episodes of weight gain, followed by weight loss) and sampled the gut microbiome of the mice to determine how weight-cycling affected the gut microbe population. As a result, they discovered that at each successive weight-loss and regain cycle, the population of microbes changed in such a way that it became easier for the mice to regain weight after dieting.
In fact, the scientists identified specific microbial populations that predisposed mice to rapid weight gain following diet. They even developed a mathematical model, or algorithm, based on gut microbiome profiles that predicted post-diet weight gain.
Because of these findings, the researchers concluded that gut microbe composition is a key driver in weight-cycling.
So, how do they do it? How does the gut microbiota accelerate weight regain after dieting?
The answer, it seems, lies in the interaction between our gut microbes and our metabolism. Remember that a common reason that people regain weight after dieting is that their metabolism slows down. Perhaps the changes in gut microbe populations alters metabolic rates and energy expenditure.
To investigate this possibility, the scientists measured the metabolic profiles of weight-cycling mice (i.e., mice that went through multiple cycles of diet-induced weight loss and subsequent weight gain) and found that certain metabolized nutrients were significantly diminished. Specifically, they found that compounds known as flavonoids (i.e., apigenin and narigenin) were degraded and depleted in weight-cycling mice.
They further showed that orally-administered flavonoids to weight-cycling mice reduced excessive secondary weight gain despite the microbiome composition. This means that therapeutic intervention with flavonoids had a protective effect against post-diet weight gain.
Flavonoids are compounds that we consume in our diet and become metabolized by our gut microbes and used by us for energy expenditure. They also have anti-oxidant and anti-inflammatory effects. So, it’s important for us to get flavonoids from our foods so that we can maintain healthy energy levels and protection from excessive inflammation and oxidation. We also need our gut microbes to work with us to make flavonoids available for our metabolic pathways.
Based on their findings, the scientists conclude that the change in gut microbe populations following weight-cycling causes flavonoids to be degraded rather than utilized by gut microorganisms. Consequently, these extremely important metabolites are not available and energy expenditure declines, resulting in accelerated weight regain.
Why is this important for me?
We’ve written about the gut microbiota in previous articles (if you’ve missed it, check out this blog post). Remember that the massive numbers of microbes in our gut are constantly competing for available nutrients. The types of foods we put through our digestive system dictates which type of microbes thrive and which microbes get pushed to the side.
For instance, if you put junk food into your system, the microbes that are good at digesting plant-based foods get shut out by the microbes that specialize in digesting junk. On the other hand, if you put healthy plant-based fiber into your system, the microbes that are good at digesting junk food get pushed aside while the beneficial plant-eating microbes thrive. We need the beneficial microorganisms that can release the healthy nutrients in plant-based foods such as flavonoids and short chain fatty acids.
In the case of the weight-cycling mice described in the above study, their gut microbiome population had changed so much after repeated dieting that they were no longer able to metabolize flavonoids in the normal fashion. As a result, energy levels declined and the mice regained weight after dieting.
The Weizmann Institute of Science study was based on a laboratory mouse model and additional studies are required to confirm these results in humans. Nevertheless, it’s safe to say that when we make drastic changes to our diet (e.g., extreme weight-loss dieting followed by unhealthy fatty diets), we change the nutritional environment in our gut. This causes changes to our gut microbiota and consequently effects how our gut microbiota metabolizes the food that we eat.
We need the trillions of microbes in our gut to work with us to extract healthy nutrients from the food we eat. It’s likely that when we lose certain beneficial microbes due to improper dieting, we can no utilize certain nutrients (i.e., flavonoids) that keep us healthy.
If you have experienced weight-cycling and have found it difficult to keep off unwanted weight, here are a few takeaway messages:
Probiotic-containing foods (i.e., kimchi and other fermented vegetables, cultured dairy, etc.) and probiotic supplements are a great way to introduce a variety of beneficial microbes to your gut. In addition, we should all seek out and consume plenty of flavonoid-containing foods. Fortunately, flavonoids are present in fruits, vegetables and legumes. Oranges, grapefruit, lemons, tomatoes, blueberries, cabbage, cherries, cranberries, onion, apples, romaine lettuce, almonds, turnip greens, quinoa, parsley, and many more tasty foods contain flavonoids.
This scientific study shows that certain populations of harmful microbes can destroy and eliminate the beneficial nutrients that we need from healthy plant-based foods. By feeding your gut microbiota with plant-based fiber (i.e., real food) and eliminating junk food and overly processed, packaged foods (i.e., fake food), you can begin to change the composition of your gut microbiota so that the microbes residing within you are working for you to improve your health.
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