The Negative Impact of Yo-Yo Dieting on Your Muscles

As you age, there is a certain amount of muscle mass loss and function that occurs in a process called sarcopenia, starting in your 30s and picking up steam with every decade. Although this is a normal progression, there are certain actions you can take to speed it up or slow it down — for example, sedentary behavior can give sarcopenia an unfortunate boost, causing as much as 5% more muscle mass loss than someone who stays active.

Another potential source of fuel for sarcopenia? Yo-yo dieting.

A new study suggests weight cycling can have a negative ripple effect when it comes to strength and function. Previous research has highlighted how yo-yo cycles are tough on health in other ways, particularly your heart, hormones and metabolism. Now, it seems you can add “muscle loss” to the list.

In the recent study, researchers looked at 60 men and 147 women, with an average body mass index (BMI) of 38 and a mean age of 52. They were categorized into three groups: non-weight cyclers, mild weight cyclers and severe weight cyclers who had more than five weight cycles during their lives.

A weight cycle was defined as a voluntary loss — meaning it was done on purpose — of more than 6.6 pounds, followed by an involuntary weight regain of that same amount, within the same year.

Although using BMI as a measure has some significant limitations, the point of this study was to look at muscle loss rather than BMI numbers. That means researchers looked beyond scale weight and BMI and instead measured muscle strength through handgrip exercises, as well as bone mineral density and percentage of lean muscle and fat mass.

They found those in the severe weight cycle group had nearly four times the increased risk of low muscle mass compared to the non-weight cycle group using the scan data and six times more risk when considering handgrip strength.

Basically, if participants had stayed at the same weight, even if they were overweight or obese, they would have had less muscle mass loss. That’s because of how the body puts that weight back on, according to lead researcher Dr. Andrea Rossi, PhD, of the Healthy Aging Center at the University of Verona.

“When you regain weight, you are almost always adding more fat than you had originally,” he said. “That can be very problematic for people who lose muscle when they lose weight, which we often see with crash diets or significant caloric restriction. Unfortunately, when the weight comes back, the muscle doesn’t come with it.”

Most people hate adding fat back on because of how it looks and feels, but what’s even worse is how it then affects your body.

Fat mass can prevent amino acids from working properly within muscle tissue, Rossi said. You don’t synthesize protein as well as you would without as much fat mass, which means muscles aren’t getting what they need to maintain or build strength.

That can put you at risk for a condition called sarcopenic obesity, which is a double-whammy situation of low muscle mass and high fat mass. And, unfortunately, this can keep getting worse if the yo-yo cycles continue.

Here’s more bad news: Yo-yo dieting also tends to build up that regained fat in your midsection, according to Candice Seti, licensed clinical psychologist, certified personal trainer and certified nutrition coach, known as The Weight Loss Therapist. That is often a sign of visceral fat, the more “dangerous” kind that wraps around your organs, and is associated with conditions like heart disease and stroke.

“With yo-yo dieting, you think you are putting time and energy into getting healthier only to end up less healthy than when you started,” Seti said.

Given the mounting evidence about the danger of weight cycling — including one study that suggests it may shorten your life — it makes sense to drop the yo-yo and focus on slower-but-sustainable strategies instead.

Obviously, focusing on good eating habits and gradual calorie reduction, plus tracking your progress on an app like MyFitnessPal, is very helpful, but what you eat should be only one part of your overall weight-loss plan, Seti suggests.

You should also focus on getting enough sleep, de-stressing when you can, hydrating more and finding a form of physical activity that works best for you. Most of all, be patient. You might not see results that are as dramatic as you would with a weight-cycling episode, but it will be far better for your health in the long run.