Yo-Yo Dieting Messes with Your Brain and Gut Microbes

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Until recently, most experts believed that yo-yo dieting, repeatedly dieting, losing weight, going off the diet, re-gaining weight, and starting the cycle again, was not implicated in causing overall “greater” weight gain. In fact, many health experts will often tell you to keep trying to lose weight even if you’ve had multiple failures. However, a study published in Evolution, Medicine and Public Health that looks at animals and weight gain, suggests that dieting repeatedly may lead to overall weight gain.

Another study published in the New England Journal of Medicine suggests that recurrent fluctuations in body weight may increase mortality and heart problems.

At the core of dieting is the problematic philosophy that you are on a diet for a temporary period of time. That means that once you get close to or hit goal weight, you can “stop the diet.” So you end up with repeated attempts to lose weight, oftentimes guided by common temporary goals like:

  • I want to look good for my wedding
  • I want to look good for my school reunion
  • I want to attract the opposite sex
  • I need to improve my health profile in order to get life insurance

There hasn’t been enough research to suggest whether cycling diets and weight loss is detrimental to one’s health or overall weight balance. This observational animal study seems to offer some interesting clues to how and why yo-yo dieting causes overall weight gain. The theory has to do with how the body responds to famine.

Past science has suggested that when you don’t eat breakfast, your metabolic rate slows down. After a night of sleep (and many hours of not eating) the body’s metabolism perceives famine, so it reacts by slowing down to limit calorie burn. It’s basically preparing to live off stores of fat in the body — until food is consumed. Similar to this principle, the study suggests that animals respond to the risk of famine (when they start to have difficulty finding food) by gaining weight. Birds in the winter become fatter when they can’t find berries and seeds. This phenomenon happens when there is no food available — it’s not that the animals stored food beforehand in preparation for the famine. In many cases, famine “just happens” and there's no warning. And yet they gain weight.

The researchers extended this theory using a mathematical model to suggest that an animal clearly knows whether food is present or not. What they don’t know is whether the situation will suddenly change. Will abundant food suddenly disappear OR will the famine suddenly resolve, and food sources appear. So the “optimal animal,” selected by nature to be fittest, has the best chance of passing on his or her genes, if they gain weight during famine. That ensures passing on a gene that guarantees survival.

Applying this theory to humans, it’s not surprising that the average weight gain for a chronic dieter is higher, because their body is being repeatedly primed for famine AND doesn’t know when food will be reintroduced. A vicious and continuous cycle of yo-yo dieting convinces the brain that it needs to instigate primal urges that will lead to storing fat. So the brain puts out powerful hunger signals that the dieter initially ignores. Ultimately, the person will abandon calorie restriction and eat large quantities of food. This cascade of events happens in yo-yo dieting because the brain is convinced that another famine is coming soon.

Recent research has also shown that rats provoked to exhibit yo-yo dieting behavior show accelerated weight gain. The study revealed that there was a change in gut microbe populations after chronic diet and weight cycling and the shift in gut microbe population seemed to cause accelerated weight gain when the rats abandoned the calorie-restricted diet. So the body’s response to repeated famine seems to cause brain signals of hyper-hunger and gut microbe changes that prime the body for weight gain.

If you want to stop the chronic dieting cycle, then what's the best way to lose weight?

  • Identify if you have an eating disorder like bulimia or EDNOS. Chronic dieting can be a sign of an eating disorder

  • Stop dieting and start eating with a two-phase mentality — a weight loss phase and maintenance phase

  • Recognize that a diet shouldn’t change dramatically — the amount of food should change. Eat less when losing weight and then introduce larger portions of the same foods when you enter the maintenance period. The Mediterranean Diet can work well for this approach

  • Recognize if you can handle treats and special food moments. Some people can have an indulgence, while for others it can start a food binge. Know your capacity and your limits when it comes to treat foods

  • Learn about probiotics and how they can help to balance gut microbes and support weight loss and better health. Seek the input of a doctor or dietitian/nutritionist. However, no probiotic has been proven to cause weight loss.

  • Set up a support team that includes friends, family, health professionals and don’t abandon this support team once you hit goal weight — that’s when you need them the most

  • Commit to an exercise program that can help to nudge weight loss and also help immeasurably when you are trying to maintain your weight -** Recognize if you respond better to dramatic changes or more gradual lifestyle modifications**. Some people need to make radical changes more quickly, but most people benefit from gradual and steady behavior changes

  • Lose the black and white mentality when it comes to “breaking your diet.” One meal, a day’s worth, or a few days of poor food choices, or too much food is not a reason to derail a commitment to your long-term eating and exercise plan. Get help from your support team and get back on track

  • Use goals to nudge your commitment but don’t make these milestone goals the end all — the main goal should be a focus on better health and quality of life

A final note: Yo-yo dieting doesn’t provide long term weight loss not because the body is primed for famine, which has not been proven, but because it simply doesn’t lead to long term caloric restriction and a healthy eating habit that can be maintained.

See more helpful articles:

Why Eating When You're NOT Hungry Is Bad for You

What to Look for in a Dietician/Nutritionist