Is a calorie just a calorie?
Short answerYes, but
On this page
Yes, for the basic math. Fat comes off when you eat fewer calories than you burn, and careful studies keep finding that the source of the calories changes the result very little at the same total. But foods are not equal in practice. Some make you eat 500 more calories a day without noticing, and some cost more to digest or keep more muscle.
What we’d do
Count calories, because the gap is what takes fat off. Then choose the calories that make the gap easy: protein at every meal, plenty of vegetables, food that still looks like it grew, and few packaged snacks and sweet drinks. The total decides the result. The food decides whether you can hold the total.
If you remember three things
- At the same calories, diets lose about the same fat.
- Processed food made people eat about 500 more calories a day without trying.
- Protein costs the most to digest and keeps the most muscle.
The two camps
One camp says calories are all that matters, so eat what you like and count. The other says calories don’t matter, only hormones and food quality. Each has half of it.
A calorie is like a dollar. A dollar is a dollar, but some stores are set up to make you spend more of them.
Where calories are just calories
When scientists fix the calories, the type of food barely changes the fat lost. On a metabolic ward in 2015, 19 adults cut 30% of their calories from carbs or from fat, and the difference in fat loss was a few dozen grams a day. In DIETFITS, 609 adults ate healthy low-carb or healthy low-fat for a year and lost about the same weight. No diet beats the math.
Where they aren’t
How much you end up eating
20 adults in an NIH clinic, two weeks on each diet. Hall and colleagues, 2019
Offered as much as they wanted, people ate about 508 more calories a day on ultra-processed food than on unprocessed food. They gained about 2 pounds in two weeks on one and lost about 2 on the other.
Small and short, but every bite was measured.
How full it keeps you
38 foods, each served as 240 calories. Holt and colleagues, 1995
Boiled potatoes kept people fullest, more than three times as full as white bread. A croissant filled them least, at under half.
Fullness over two hours, not over a diet.
What digestion costs
Review of diet-induced thermogenesis. Westerterp, 2004
Digesting protein uses 20 to 30% of its calories, carbs 5 to 10% and fat 0 to 3%.
On a mixed diet the total cost is about 10% of what you eat.
What you lose
40 young men in a 40% calorie cut, 4 weeks. Longland and colleagues, 2016
On high protein they gained about 2.6 pounds of lean mass and lost more fat than on lower protein, at the same calories.
Young men training six days a week.
Why counting still fails people
Counting only works if the count is right. In a 1992 study of 10 people who said they couldn’t lose weight on very few calories, they had underreported their food by 47%. Most stalls come from calories that never made it into the log, which is why the foods that are hard to overeat help so much.
More detail: the label number
The calories on a label are an estimate of the energy your body can get from a food. The cost of digesting it differs by protein, carbs and fat, as above. That effect is real and small next to the effect of simply eating more or less. That’s the yes in yes, but. The but is everything that decides how much you eat.
7 sources
- Hall et al., Calorie for calorie, dietary fat restriction results in more bodyfat loss than carbohydrate restriction in people with obesity, Cell Metabolism, 2015pubmed.ncbi.nlm.nih.gov
- Gardner et al., Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion (DIETFITS), JAMA, 2018pubmed.ncbi.nlm.nih.gov
- Hall et al., Ultra-processed diets cause excess calorie intake and weight gain: an inpatient randomized controlled trial of ad libitum food intake, Cell Metabolism, 2019pubmed.ncbi.nlm.nih.gov
- Westerterp, Diet induced thermogenesis, Nutrition and Metabolism, 2004pmc.ncbi.nlm.nih.gov
- Holt et al., A satiety index of common foods, European Journal of Clinical Nutrition, 1995pubmed.ncbi.nlm.nih.gov
- Longland et al., Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss, American Journal of Clinical Nutrition, 2016pubmed.ncbi.nlm.nih.gov
- Lichtman et al., Discrepancy between self-reported and actual caloric intake and exercise in obese subjects, New England Journal of Medicine, 1992pubmed.ncbi.nlm.nih.gov
