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Can yo-yo dieting kill your metabolism?

When I ask clients what diet(s) they have tried in the past, the common response is: “What haven’t I tried?” or “You name it, I’ve tried it.” And they are concerned that they have permanently damaged their metabolism. I hear statements like, “I’m here to fix my broken metabolism,” or “All this dieting has ruined my metabolism.” So is it true? Does yo-yo dieting permanently damage one’s metabolism?

 

As usual, let’s look to the science!

 

A study conducted by Wadden and colleagues (1992) at the University of Pennsylvania School of Medicine investigated this question. They took 50 obese women with a mean age of 40 years, and each weighing approximately 225 lb. and about 5”4’ tall.

 

The women all consumed 1,200 calories per day at the start of the study, and were then randomly assigned to one of three very low-calorie diet groups (420 calories per day, 660 calories per day, or 800 calories per day) for 11 weeks. After the 11 weeks, each participant consumed a balanced diet of 1,000 to 1,500 calories for five weeks. And here is what happened!

 

Wadden et al. found that weight cycling (repeatedly losing and regaining weight) had NO EFFECT on metabolism! Moreover, they also found NO increases in depression, disordered eating, or percentage of weight as fat.

 

In other words, weight cycling does NOT metabolically impact the success of future dieting. That’s good news. However, there are other reasons why we don’t want to weight cycle. We want to lose weight and keep it off. So if yo-yo dieting doesn’t permanently damage the metabolism, why is it so hard to keep the weight off?

 

There are a multitude of factors that can make weight management difficult, and I am only going to address one issue here: Metabolism will always match the circumstance. When I gain weight, my metabolism becomes inefficient. When I lose weight, my metabolism becomes efficient.

 

In terms of energy usage (burning calories), inefficiency means that I use more energy (calories) for any given task, including maintaining my basic body functions. The opposite is true for efficiency: My body requires less energy (calories) to do tasks and maintain itself.

 

When we lose weight, we require less energy (calories) over time. When we gain weight, our bodies require more energy to do tasks and maintain themselves. This is why we plateau as we gain weight, and we plateau when we lose weight. This is normal, and it is also why conventional diets can be so ineffective. As coaches, our job is to help you understand the science of the body, and also to give you the tools you need to help manage the circumstances.

 

So lean into the scientific truth, equip yourself with the understanding of how your body behaves under certain circumstances, and get the tools you need to help manage those changes!

 

When we lose weight, there are things that can help us manage the fact that metabolism becomes more efficient. One of these things is exercise. Exercise is one of the best weight-management tools we have–not a great weight loser, but a GREAT weight manager.


Reference:

Wadden, Thomas A., et al. “Relationship of dieting history to resting metabolic rate, body composition, eating behaviour, and subsequent weight loss.” American Journal of Clinical Nutrition, July 1992; Vol. 56, No. 1, pp 203S-208S.

 

Jason Hagen