How Many Calories Are in a Pound of Fat?
A pound of body fat holds about 3,500 to 3,750 calories, or roughly 7,700 to 8,300 per kilo. The well-known rule, from the 1950s, says it takes a 3,500 calorie cut to lose a pound of weight. That’s a fair starting point. But it overestimates how much weight you’ll lose over time, because your body changes as you lose weight.
In brief
- The 3,500 calories per pound rule comes from a 1958 paper by Max Wishnofsky.
- Cut one can of fizzy drink a day and the rule says you'll lose 15 lb in a year. Newer estimates in a 2014 paper put it at about 6 to 8 lb.
- Early in a diet, a pound of weight comes off for fewer calories, because more of it is water and stored carbs.
- Use the rule for a first target, then let your weight trend guide you.
Where does the 3,500 calorie rule come from?
The 3,500 calorie rule comes from Max Wishnofsky, who worked it out in 1958. He wanted a simple answer to how many calories a pound of body weight is worth.
Body fat isn’t pure fat. About 87% of it is fat, and the rest is water and other tissue. Pure fat holds about 9.5 calories per gram. That works out at about 3,750 calories in a pound of body fat. Wishnofsky then checked this against a diet study from 1930 and settled on 3,500 calories per pound of weight lost.
How many calories do you need to cut to lose a pound?
By the rule, you need to cut 3,500 calories to lose a pound, or 500 a day for a week. In practice the number changes as you go.
In the first few weeks, a pound comes off for fewer calories than that. A 2014 paper by Thomas and colleagues explains that early weight loss includes more water, stored carbs and protein, which hold fewer calories than fat. Later, more of what you lose is fat, so the number rises.
| Estimate | Calories per pound lost |
|---|---|
| What the rule says | About 3,500 |
| First 4 weeks of a diet | About 2,200 |
| By 6 months | About 3,000 |
The last two figures are from a 6-month study of people on strict diets, as reported in the 2014 paper.
That’s also why the first weeks of a diet often look so good on the scale, as we explain in when will a calorie deficit show on the scale.
Why doesn’t the 3,500 calorie rule work over time?
The 3,500 rule assumes the gap between what you eat and what you burn stays the same. As you lose weight, your body burns less, so the same cut does less each week. Researchers Hall and Chow called this the most serious error in the rule. It’s one reason weight loss slows down, which we cover in weight loss plateau: why has it stopped.
Say you’re a 30-year-old woman weighing 12 stone (76 kg), and you swap one can of fizzy drink, about 140 calories, for water every day. The 3,500 rule says you’d lose about 15 lb in a year. Newer estimates that allow for your body changing put it at about 6 to 8 lb.
The longer you diet, the bigger the gap. In the same 6-month study, the rule overestimated weight loss by about 24 lb (11 kg) on average.
Does it depend on how much body fat you have?
It seems to. The rule fits better for people with more body fat to start with.
Kevin Hall’s 2008 model suggests the rule roughly fits people starting with a lot of body fat, more than about 30 kg (66 lb). If you’re leaner, a pound of weight comes off for fewer than 3,500 calories. That’s because more of what leaner people lose is muscle and water, which hold fewer calories than fat.
This may help explain why men can lose more weight than women on the same diet. Women tend to carry more body fat at the same weight, so more of what they lose is fat, which takes more calories to shift. Our post on why two people lose weight at different rates covers other reasons.
How should you use the 3,500 calorie rule?
Use it to get started, then let your weight trend guide you.
- Set a first target with our calorie deficit calculator. Trying to gain? Use our weight gain calculator.
- Expect a faster drop in the first week or two.
- Weigh at the same time of day. Daily weigh-ins with a weekly average work well, but once a week is fine too.
- Every few weeks, check your trend. If your weight has stalled, your body may now need less.
- Re-run the calculator with your new weight, then check again in a few weeks.
If food or weight is starting to worry you, it’s fine to step back, and your GP can help.
Where Ori fits
Ori gives you a starting target. With Premium, Ori checks your weight trend each week before it suggests a new target, so it keeps up as your body changes. If the numbers stress you out, Stealth Health, which is free, hides them and tells you how things are going in plain words. You can try Ori here.
Related reading
- How do I find my maintenance calories?
- Water weight vs fat: how to tell the difference
- Why your calorie target shouldn’t stay the same
Sources
- Thomas DM, Gonzalez MC, Pereira AZ, Redman LM, Heymsfield SB. Time to correctly predict the amount of weight loss with dieting. Journal of the Academy of Nutrition and Dietetics, 2014. Describes Wishnofsky’s 1958 rule and the CALERIE I study figures.
- Hall KD. What is the required energy deficit per unit weight loss? International Journal of Obesity, 2008.
- Hall KD, Chow CC. Why is the 3500 kcal per pound weight loss rule wrong? International Journal of Obesity, 2013.
A gentle safety note
Ori supports general wellness. It is not medical care. If you have a history of disordered eating, are pregnant or breastfeeding, take medicines that affect weight or appetite, or have a clinical nutrition need, speak with a qualified healthcare professional before changing your intake or weight goal.
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