Maintaining a body weight of 300 pounds requires roughly 2,300 to 3,500 calories per day for most people, depending on sex, age, height, and how physically active you are. That’s a wide range because these factors make a real difference. A 35-year-old man who’s 5’10” and lightly active needs about 3,300 calories, while a 50-year-old woman who’s 5’5″ and sedentary needs closer to 2,300. Below, you’ll find the math broken down so you can estimate your own number.
Your Resting Metabolic Rate at 300 Pounds
The starting point is your resting metabolic rate (RMR), the calories your body burns just to keep you alive: breathing, circulating blood, regulating temperature, and running all your organs. This accounts for the largest chunk of your daily calorie burn, typically 60 to 75 percent of the total.
The formulas used most often in clinical settings come from Cleveland Clinic and work in pounds and inches:
- Males: RMR = (4.38 × weight in pounds) + (14.55 × height in inches) − (5.08 × age) + 260
- Females: RMR = (3.35 × weight in pounds) + (15.42 × height in inches) − (2.31 × age) + 43
Plugging in 300 pounds with some common heights and ages gives you a baseline:
- Male, 5’10”, age 35: RMR ≈ 2,415 calories
- Male, 5’10”, age 50: RMR ≈ 2,340 calories
- Female, 5’5″, age 35: RMR ≈ 1,970 calories
- Female, 5’5″, age 50: RMR ≈ 1,935 calories
Notice that sex creates the biggest gap. Men carrying 300 pounds burn several hundred more calories at rest than women at the same weight, primarily because of differences in muscle mass and hormonal profiles. Age matters less than you might expect, shaving off roughly 75 to 100 calories between age 35 and 50.
How Activity Changes the Total
Your RMR is just the floor. On top of that, you burn calories through every movement you make, from walking to the kitchen to exercising at a gym. Researchers use a set of standard multipliers to estimate total daily energy expenditure (TDEE):
- Sedentary (desk job, little to no exercise): RMR × 1.2
- Lightly active (light exercise 1 to 3 days per week): RMR × 1.375
- Moderately active (moderate exercise 3 to 5 days per week): RMR × 1.55
- Very active (heavy exercise 6 to 7 days per week): RMR × 1.725
For the 35-year-old male example above with an RMR of 2,415, the maintenance calories look like this: about 2,900 if sedentary, 3,320 if lightly active, and 3,745 if moderately active. For the 35-year-old female with an RMR of 1,970, the numbers come out to roughly 2,365 sedentary, 2,710 lightly active, and 3,055 moderately active.
One thing worth noting: at 300 pounds, your body is already doing more work than a lighter person’s body during any movement. Walking across a parking lot at 300 pounds burns meaningfully more calories than the same walk at 180 pounds, simply because you’re moving more mass. So even a sedentary lifestyle at this weight burns more total calories than a sedentary lifestyle at a lower weight.
Why These Estimates Can Be Off
A systematic review published in the Journal of the American Dietetic Association found that the Mifflin-St Jeor equation (which the formulas above are based on) is the most reliable option available, predicting resting metabolic rate within 10 percent of the actual measured value for most people. But “most people” still leaves room for individual error, and that 10 percent margin means your true number could be 200 to 300 calories higher or lower than the formula suggests.
The accuracy tends to decrease for people in groups that were underrepresented in the original research, including certain age ranges and ethnic backgrounds. If you’ve been eating at what should be your maintenance calories and your weight is consistently drifting up or down, the formula may not be capturing your individual metabolism well. In a clinical setting, the gold standard is indirect calorimetry, a test where you breathe into a device that measures your actual oxygen consumption and carbon dioxide output to calculate your precise metabolic rate.
Metabolic Adaptation After Weight Loss
If you previously weighed more and lost weight down to 300 pounds, your calorie needs may be somewhat lower than the formula predicts. This phenomenon, called metabolic adaptation, means your body burns fewer calories than expected for your current size after a period of weight loss. In a practical example: someone who lost weight to reach 198 pounds was found to need 2,000 calories per day instead of the predicted 2,200, a gap of about 200 calories.
Interestingly, research from the University of Alabama at Birmingham has found no evidence that metabolic adaptation actually causes weight regain. People with greater metabolic adaptation did take longer to reach weight loss goals and lost less total fat in response to a calorie-restricted diet, and a 2023 study found it was associated with greater increases in appetite. But the adaptation itself didn’t predict whether someone regained weight over a two-year follow-up. So while the calorie math might shift slightly, the effect isn’t the insurmountable barrier it’s sometimes made out to be.
What Those Calories Should Look Like
Calorie quantity is only part of the picture. About 10 percent of the calories you eat get burned just through digestion itself, a process called the thermic effect of food. Protein has the highest thermic effect of any macronutrient, meaning your body spends more energy digesting protein than it does digesting fat or carbohydrates. This is one reason protein intake matters for weight maintenance beyond just muscle preservation.
The baseline recommendation for protein is 0.36 grams per pound of body weight, which at 300 pounds would come out to about 108 grams per day. However, that’s the minimum to prevent deficiency, not necessarily the optimal amount for someone maintaining a higher body weight. Many nutrition experts suggest higher intakes for people with obesity because the standard per-pound calculation can overshoot when a large proportion of body weight is fat rather than lean tissue. A more practical approach is to aim for 100 to 130 grams of protein daily, spread across meals, rather than trying to hit a strict per-pound target based on total body weight.
Tracking Your Actual Maintenance Number
Formulas give you a starting point, not a final answer. The most reliable way to find your true maintenance calories is to track your intake consistently for two to three weeks while weighing yourself at the same time each day (first thing in the morning works best). If your average weight stays stable over that window, your average daily intake is your maintenance number. If you’re gaining, you’re eating above maintenance. If you’re losing, you’re below it.
Daily weight fluctuates by 2 to 5 pounds due to water retention, sodium intake, and digestive contents, so don’t react to any single day’s reading. Look at the weekly average instead. After two or three weeks of data, you’ll have a far more accurate picture of your personal calorie needs than any equation can provide.