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You’ve worked hard to lose weight. But keeping it off feels harder than you expected. You’re hungry more often, and the habits that helped you lose weight no longer seem to be enough.
There’s a biological reason this can happen.
After weight loss, your body needs less energy. Sometimes, though, it also starts conserving energy beyond what its smaller size would explain. This is called metabolic adaptation, and it can make maintaining weight loss more challenging.
In this episode of Metabolic Classroom, Dr. Ben Bikman explains what researchers learned from The Biggest Loser, why the body responds this way, and what can help support long-term weight maintenance.
Why A Smaller Body Burns Fewer Calories
Your body uses energy around the clock—to keep your heart beating, your brain working, and your tissues alive.
A larger body generally needs more energy to do those things. When you lose weight, there’s less tissue to maintain, so your daily energy needs naturally decrease.
Losing muscle can contribute to that decrease. But muscle loss doesn’t explain everything. Your body can also adjust how much energy it uses, becoming more efficient and burning fewer calories than expected.
What Researchers Found After The Biggest Loser
Contestants on The Biggest Loser lost large amounts of weight through intense exercise and severe calorie restriction.
When researchers followed up with 14 contestants six years later, the participants had regained much of the weight they had lost. Yet their resting metabolism remained lower than expected.
On average, they were burning about 500 fewer calories per day at rest than researchers predicted for their body composition and age. That was an additional slowdown beyond what changes in body size could explain.
This was a small study of an extreme weight-loss program. It doesn’t mean everyone who loses weight will experience the same response, or that weight regain is inevitable. It does show that the body’s adjustments can persist long after a diet ends.
Why Hunger Rises As Energy Use Falls
One important part of this response involves leptin, a hormone made by fat cells.
Leptin helps tell your brain how much energy you have stored. As you lose body fat, leptin levels fall. Your brain can interpret that change as a reason to conserve energy and increase hunger.
That creates a difficult combination: you feel a stronger pull to eat while your body needs fewer calories.
Research has shown that restoring leptin to pre-weight-loss levels can reverse several of these energy-conserving changes under controlled conditions. This helps explain leptin’s role; it doesn’t make leptin a routine weight-loss treatment.
What Can Help During Weight Loss And Maintenance?
There’s no guaranteed way to prevent metabolic adaptation. But there are useful ways to support your muscle, activity, and eating habits.
- Make protein a priority. Include protein-rich foods in your meals. A review of weight-loss trials found that higher-protein diets helped preserve more lean tissue and reduced the decline in resting energy expenditure compared with standard-protein diets.
- Include strength training. Preserving muscle is an important part of losing weight well. Resistance training gives your muscles a reason to stay strong while you lose fat.
- Keep moving throughout the day. Walking, household tasks, and other everyday movement contribute to the energy you use outside formal exercise.
- Plan for life after weight loss. Choose eating and activity habits you can continue. Reaching a goal weight starts a new phase that deserves ongoing attention and support.
These habits can help, but they don’t guarantee that your metabolism will return to its previous level.
Does Eating Fewer Carbohydrates Make A Difference?
Dr. Bikman also explores research on carbohydrate intake during weight maintenance.
One controlled feeding trial reported higher daily energy expenditure on a lower-carbohydrate diet after weight loss. However, other researchers have challenged the size and reliability of that effect. The evidence does not establish that cutting carbohydrates will reverse metabolic adaptation.
For everyday eating, the episode emphasizes protein-rich meals and reducing reliance on refined carbohydrates. Any eating approach also needs to be practical enough to maintain.
If Keeping Weight Off Has Been Difficult
Difficulty maintaining weight loss can reflect real changes in hunger and energy needs. Understanding those changes can help you set more realistic expectations and build a plan that supports you over time.
Watch the full episode above as Dr. Bikman walks through the research, explains the hormones involved, and discusses how to approach weight loss with long-term maintenance in mind.