Your metabolism is not a fixed setting, and several factors can genuinely slow it down. Whether you’re trying to gain weight or simply curious about what drives your body’s energy burn rate, understanding what raises and lowers metabolism gives you practical levers to work with. The most powerful factors are how much you eat, how much muscle you carry, how active you are throughout the day, and the temperature of your environment.
Why Your Body Burns Calories the Way It Does
Your total daily calorie burn has three main components: your resting metabolic rate (the energy your body uses just to keep you alive), the calories burned digesting food, and all physical activity from workouts to fidgeting. Resting metabolism alone accounts for roughly 60 to 70 percent of total energy expenditure for most people, which is why it gets so much attention.
What determines that resting burn rate comes down to your body composition, hormones, and how much fuel you’re giving your body. Organs like the brain, liver, and kidneys are metabolically expensive, burning around 240 calories per kilogram per day. Muscle and fat tissue burn far less, between 4 and 15 calories per kilogram daily, but because you carry so much more of them, they still matter a great deal for your total burn.
Eat Less and Your Metabolism Will Follow
The single most reliable way to lower your metabolic rate is to eat fewer calories over a sustained period. When you restrict calories, your body responds by dialing down energy expenditure to match the reduced fuel supply. This process, called adaptive thermogenesis, kicks in fast. In one clinical study, participants showed an average metabolic slowdown of about 178 calories per day after just one week of calorie restriction, independent of any weight they had lost.
This slowdown happens through a cascade of hormonal shifts. As you eat less and lose fat, your leptin levels drop. Leptin is a hormone produced by fat cells that signals your brain about your energy stores. When leptin falls, the brain interprets it as a survival threat and responds by increasing hunger, reducing the drive to move, and suppressing thyroid hormone output. Since thyroid hormones set your basal metabolic rate, lower levels directly reduce the amount of energy your body uses at rest.
At the cellular level, calorie restriction slows the rate at which your cells break down glucose and fat for energy. Your body becomes more efficient, extracting more from less. This is why people who diet aggressively often hit plateaus: their metabolism has adjusted downward to protect against further weight loss. For someone actively trying to lower their metabolism, consistent moderate undereating will produce this effect over weeks.
Lose Muscle to Burn Fewer Calories
Muscle tissue is more metabolically active than fat. Losing muscle mass will lower your resting metabolic rate, though the effect per pound is smaller than many fitness sources claim. Based on clinical modeling, each kilogram of fat-free mass (which is mostly muscle) contributes roughly 19 calories per day to your resting burn rate. That means losing about 5 kilograms (11 pounds) of muscle would reduce your resting metabolism by close to 100 calories daily.
You lose muscle by avoiding resistance training, eating insufficient protein, or staying in a prolonged calorie deficit without exercise. During significant weight loss, some muscle loss is nearly inevitable unless you actively work to prevent it through strength training and adequate protein intake. If your goal is a slower metabolism, doing the opposite, skipping weights and eating less protein, will accelerate muscle loss alongside fat loss.
Move Less Throughout the Day
The calories you burn through everyday non-exercise movement, things like walking, standing, fidgeting, and doing chores, can vary enormously between people. Someone with a desk job burns up to 700 calories per day from this kind of movement. Someone who works on their feet can burn up to 1,400 calories, and a person doing physical labor can hit 2,000 or more. That gap of 1,500 calories per day between a sedentary and physically active occupation is larger than most people’s entire workout.
Sitting more, driving instead of walking, and generally reducing your daily movement will lower your total energy expenditure significantly. In one study of women on a calorie-restricted diet, those who didn’t exercise saw their non-exercise activity thermogenesis drop by 150 calories per day, a 27 percent reduction from their starting point. Your body naturally dials back the urge to move when fuel is scarce, which compounds the metabolic slowdown from dieting.
Stay Warm
Your body burns extra calories to maintain its core temperature in cool environments. Research comparing metabolic rates at different room temperatures found that resting energy expenditure was significantly higher at 18°C (64°F) and 22°C (72°F) compared to 28°C (82°F), which falls within the thermoneutral zone for most people. At 28°C and above, up to 38°C (100°F), metabolic rates stayed low because the body didn’t need to generate extra heat.
If you want to minimize calorie burn, keeping your environment warm, wearing layers, and avoiding cold exposure will eliminate the extra energy cost of thermoregulation. This effect is modest compared to diet and activity changes, but it’s a real and measurable contributor.
What Happens to Metabolism With Age
A common belief is that metabolism drops sharply in your 30s or 40s, but a large-scale study published in Science found that metabolic rate, adjusted for body size and composition, stays remarkably stable from your 20s through your 50s. The real decline doesn’t begin until after age 60, and even then it’s gradual, only about 0.7 percent per year.
The weight gain most people experience in middle age is more about changes in activity level, muscle mass, and eating habits than a mysterious metabolic slowdown. If you’re in your 30s or 40s and feeling like your metabolism has crashed, the explanation is more likely a shift toward less movement and more calories than an age-related change in your cells.
Is a Slower Metabolism Reversible?
One important thing to understand: metabolic slowdowns from dieting are largely reversible. The idea of permanent “metabolic damage” from restrictive eating has been a persistent concern, but research suggests it doesn’t hold up. A study in The American Journal of Clinical Nutrition found that metabolic adaptation measured right after weight loss was cut in half, to roughly 50 calories per day, once people stabilized at their new weight. When compared to people of the same size who had never dieted, those who had lost weight showed no meaningful difference in resting metabolic rate.
This means that if you lower your metabolism through calorie restriction and then return to eating more, your metabolic rate will climb back up. The adaptation is a temporary response to energy scarcity, not a permanent reprogramming. For people trying to slow their metabolism long-term, this means you’d need to maintain the conditions that produced the slowdown, whether that’s lower calorie intake, less muscle mass, or reduced activity.
Practical Approach for Slowing Metabolism
If you’re trying to lower your metabolic rate because you struggle with an uncomfortably fast metabolism or unwanted weight loss, combining several of these factors will produce the most noticeable effect. Reducing overall physical activity, especially daily non-exercise movement, has the largest practical impact on total calorie burn. Eating at or slightly below your energy needs will trigger hormonal adaptations that further reduce your resting rate. Keeping your living space warm and avoiding cold exposure removes the thermoregulation cost.
Keep in mind that many of these strategies, particularly muscle loss and extreme inactivity, carry significant health trade-offs. Muscle mass protects your joints, supports bone density, and improves metabolic health in ways that go well beyond calorie burn. A more sustainable path for someone struggling to maintain weight is usually to increase calorie intake rather than to deliberately suppress metabolism.