investigating "the broken metabolism"
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Arnold Schwarzenegger <[email protected]>
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Arnold's Pump Club investigates the concept of a "broken metabolism" and its relation to dieting and weight loss. The campaign explores whether dieting can ruin one's metabolism, citing a study where participants' resting metabolism slowed after an 8-week diet. It aims to provide insights on weight regain and lasting weight loss results.
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Does Dieting Ruin Your Metabolism?
After an 8-week diet, metabolism ran more than 100 calories below predicted levels. A year later, things changed in a big way. Here’s what to know about weight regain and weight loss results that last.
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Today’s Health Upgrade
Let’s talk about your “broken metabolism”
The pillow variable most people overlook
Adam’s corner: It’s still here
Fact Or Fiction
Does Dieting Break Your Metabolism?
You do everything right for five weeks, and the scale won’t move. In those moments, it’s easy to blame your metabolism. Or wonder if something you did in the past has messed up your future.
Think of your body as a parked car that still burns gas. Lose weight, and you become a smaller car that needs less fuel. During a diet, your body may conserve a little more energy. The question is whether this extra slowdown lasts.
Metabolism does slow during weight loss, but a well-controlled study suggests most of that additional slowdown fades after you stop dieting. More importantly, it doesn’t appear to explain who regains weight.
A team of researchers put adults with obesity on a 1,000-calorie-per-day meal-replacement diet for eight weeks. The participants lost about 30 pounds, then increased their calories enough to maintain their new weight. Researchers compared each person’s resting metabolism with what someone of the same size would be expected to burn.
Among the 45 participants tracked for a full year, resting metabolism was 107 calories per day below predictions immediately after the diet. In other words, when weight drops, resting metabolism is supposed to decrease. But initially, the drop is bigger than expected.
However, four weeks later, the gap had fallen to just 49 calories. After a year, it was just 7 calories, which is basically no difference.
On average, participants had regained about nine pounds by then (roughly 30% of what they lost), even with monthly check-ins.
But the people whose metabolism slowed the most weren’t more likely to regain weight.
That doesn’t mean a “broken metabolism” is impossible. It can happen, but it’s more unlikely and regulates over time.
So what causes regain? The bigger force appears to be appetite.
In a year-long study of adults with type 2 diabetes, researchers estimated that for every 2.2 pounds lost, people ate about 100 more calories per day than before. That’s more than three times the drop in calories burned, which is why keeping weight off requires a plan for hunger (protein, fiber, sleep, and activity), not just a lower calorie target.
That doesn’t mean metabolic adaptation is imaginary. Some people experience a greater slowdown than others, which can extend the time it takes to reach a goal, and other studies have reported longer-lasting slowdowns. This study also measured only resting metabolism, so it doesn’t tell us what happened to calories burned through daily movement.
Still, the average additional slowdown was relatively small (roughly the calories in a tablespoon of peanut butter), and most of it disappeared once the participants stopped actively dieting.
If progress stalls, start by updating your calorie target. A smaller body naturally burns less, so recalculate approximately every 10 pounds you lose.
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