A truly “high metabolism” means your body burns through calories faster than average, making it hard to gain or maintain weight. For most people, this isn’t a fixed trait you’re stuck with. It’s the result of specific, changeable factors like activity level, diet composition, body composition, and sometimes an underlying medical condition like hyperthyroidism. The approach depends on what’s driving your metabolic rate up in the first place.
Rule Out a Medical Cause First
The most common medical reason for an abnormally high metabolism is hyperthyroidism, a condition where the thyroid gland pumps too much hormone into the bloodstream. Thyroid hormones affect every cell in your body. They control how fast you burn fats and carbohydrates, influence your heart rate, and regulate protein production. When levels are too high, your entire system runs hot.
Graves’ disease, an autoimmune condition where the immune system attacks the thyroid gland, is the most common cause of hyperthyroidism. Overactive thyroid nodules (noncancerous lumps that produce excess hormone) and thyroid inflammation that leaks stored hormone into the bloodstream can also be responsible. If you’re losing weight without trying, feeling jittery, sweating more than usual, or noticing a rapid heartbeat, these are classic signs that your thyroid may be overproducing. A simple blood test can confirm it.
When hyperthyroidism is the culprit, treating the thyroid condition directly brings metabolic rate back to normal. Medications work by blocking the thyroid gland from producing excess hormones, and most people see improvement within weeks. Radioactive iodine therapy and surgery are other options depending on severity. The point is that if a medical condition is driving your metabolism, no amount of dietary change will fix it on its own.
Eat in a Consistent Caloric Surplus
If you’ve ruled out medical causes, the core strategy is straightforward: eat 300 to 500 more calories per day than your body burns. This range promotes slow, steady weight gain without overwhelming your digestive system. Gaining weight gradually is healthier than trying to pack on pounds quickly, which tends to add more fat than muscle and can stress your metabolism further.
Figuring out your baseline calorie needs is the first step. The Mifflin-St Jeor equation is the most accurate widely available formula, shown to predict resting metabolic rate within 10% of lab-measured values in most adults. Online calculators using this formula will give you a starting number based on your age, height, weight, and activity level. Add 300 to 500 calories on top of that, and you have your daily target.
Eating small meals every three to five hours, with snacks in between, makes it easier to hit that target without feeling stuffed. Many people with fast metabolisms struggle to eat large portions in one sitting, so spreading intake across the day is more sustainable than forcing three massive meals.
Choose Calorie-Dense Foods
Not all calories are created equal when you’re trying to overcome a high metabolism. A giant salad might be nutritious, but it fills your stomach without delivering many calories. The goal is to get more energy into less volume. Nuts are one of the most efficient options: a single ounce of almonds, pistachios, or walnuts packs 160 to 200 calories along with heart-healthy fats. Trail mix combining nuts with dried fruit is even more calorie-dense.
Simple swaps make a big difference without changing what you eat entirely. Cooking oatmeal with whole milk instead of water adds about 80 calories. Drizzling olive oil over salads or adding half an avocado adds another 80 or more. Spreading peanut butter on apple slices as a snack adds roughly 100 calories. These small additions compound across a day.
Liquid calories are another useful tool. Adding whole milk to coffee, drinking 100% fruit juice, or blending smoothies with protein powder (whey, pea, or hemp) lets you take in significant calories without the fullness that solid food creates. A well-made smoothie with nut butter, banana, whole milk, and protein powder can easily exceed 500 calories in a single glass.
Shift Your Macronutrient Balance Toward Fats
Different nutrients cost your body different amounts of energy to digest, a phenomenon called the thermic effect of food. Protein is the most metabolically expensive: your body uses 15 to 30% of protein calories just to digest and process it. Carbohydrates cost 5 to 10%. Fats cost almost nothing, at 0 to 3%.
This doesn’t mean you should avoid protein. Protein is essential for building muscle and overall health. But if your goal is to retain as many calories as possible from what you eat, shifting some of your intake toward healthy fats (olive oil, avocado, nuts, fatty fish, butter) means less of your food gets burned during digestion. A tablespoon of olive oil delivers 120 calories, and your body keeps nearly all of them.
Rethink Your Exercise Routine
Cardio is the most efficient way to burn calories, which is exactly what you don’t want when trying to slow a high metabolism. Endurance activities like running, cycling, and swimming demand enormous energy and tend to lean you out rather than add mass. If you’re doing a lot of cardio and struggling to maintain weight, cutting back is one of the most impactful changes you can make.
Strength training is a different story. While it burns fewer calories per session than cardio, it builds muscle, and muscle is metabolically active tissue. This might seem counterintuitive since muscle burns more calories at rest than fat does. But the trade-off is worth it: muscle adds body weight, improves your physique, and the calorie increase from added muscle is modest (roughly 6 to 7 calories per pound of muscle per day). The net effect of replacing cardio with strength training is usually a lower total daily calorie burn plus a higher, healthier body weight.
One thing to be aware of: intense strength workouts create an afterburn effect where your body continues burning extra calories for up to 48 hours after the session. This is normal and not large enough to offset the benefits of building muscle, but it does mean you need to eat accordingly on training days.
Prioritize Sleep
Sleep is one of the most underappreciated factors in metabolic regulation. Getting less than seven hours per night disrupts the hormones that control hunger and energy use. Sleep deprivation increases ghrelin (the hormone that makes your stomach growl and drives appetite) while decreasing leptin (the hormone that signals fullness). You’d think more hunger would help someone trying to gain weight, but the reality is messier. Poor sleep also raises cortisol levels throughout the day, and sustained high cortisol promotes fat storage specifically around the belly while increasing insulin resistance.
Consistently poor sleep also creates a cycle that’s hard to break. Elevated daytime cortisol increases stress, food cravings (usually for high-sugar, low-nutrient foods), and further insomnia. Over time, this disrupts metabolic health in ways that go far beyond weight. If you’re sleeping less than seven hours, improving sleep quality may do more for your metabolism than any dietary tweak.
Address Low Appetite Directly
Many people with high metabolisms don’t just burn calories fast. They also struggle with low appetite, which makes eating enough feel like a chore. A few targeted strategies can help.
Nutrient deficiencies sometimes suppress appetite without any other obvious symptoms. Zinc deficiency in particular can reduce appetite and dull your sense of taste, making food less appealing. Thiamine (vitamin B1) deficiency both decreases appetite and increases resting energy expenditure, a double hit for someone already struggling to gain weight. If you suspect either, a basic blood panel can check levels, and supplementation often restores normal appetite within a few weeks.
Fish oil supplements have shown some ability to increase appetite and reduce feelings of fullness after meals. Cooking with aromatic spices, eating meals in a social setting, and simply plating food attractively can also stimulate the desire to eat. These sound like small details, but when the core challenge is getting enough food in, anything that makes eating more appealing matters.
What Actually Changes Metabolic Rate
Your basal metabolic rate is determined largely by your age, sex, body size, and body composition. You can’t change your age or sex, but you can influence the others. As you gain weight (especially muscle), your metabolism will naturally adjust upward somewhat, but your total energy balance will still improve if your calorie intake rises faster than your metabolic rate does.
Metabolism also naturally slows with age. Someone in their teens or twenties burning through everything they eat will likely find this eases in their thirties and forties as hormonal shifts and natural loss of muscle mass reduce resting energy expenditure. This isn’t a strategy so much as a reality: the metabolism you’re fighting against right now is unlikely to stay this high forever.
The most effective approach combines several of the strategies above. Eat in a moderate caloric surplus using calorie-dense foods, shift toward more dietary fat, replace excessive cardio with strength training, sleep at least seven hours, and address any appetite or nutrient issues. None of these changes is dramatic on its own, but together they create consistent conditions for your body to hold onto the energy you give it.