Do you have to count calories to lose weight?

Short answer

No. People who only set eating hours without counting lost weight over 12 months with no difference from those who counted, and logging only high-calorie foods made no difference either. Calorie counting is one of several tools for eating less.

Do you have to count calories to lose weight?
'Count calories → eat less → lose weight' — does this formula hold?
A common belief: to lose weight, you have to count the calories in everything you eat. We checked step by step whether counting itself is what drives weight loss, or whether other methods work too.
People who logged lost more
Those who opened their food log more often lost more
142 people logged what they ate online for 24 weeks. Those who lost 5% or more of their weight opened their log 2.4 times a day; those who didn't, 1.6 times. Logging time fell from 23.2 minutes a day in month 1 to 14.6 minutes in month 6.
But the numbers people wrote were wrong
They logged 47% less than they ate
10 people who said they ate little but couldn't lose weight were measured closely for 14 days. The calories their bodies burned were normal. Instead, they logged on average 47% less food than they ate and 51% more exercise than they did. That is like eating 2,000 kcal a day and writing down about 1,060 kcal.
Just installing an app didn't work
After 6 months the difference was 0.30 kg
Out of 212 people, 105 got help installing a calorie-counting app. After 6 months, their weight change differed from the no-app group by 0.30 kg, with no meaningful difference. App logins dropped sharply after the first month.
What about simpler logging?
Logging only high-calorie foods made no difference
72 people spent 6 months either counting every calorie or logging only high-calorie foods like sweets, fried food, sugary drinks and alcohol, with a limit of 3-5 a day. They lost 5.7% and 4.0% of their weight, with no difference. In a study of 38 people it was 3.4 kg vs 3.3 kg, again no difference, and the simple group logged on 97% of days vs 49% for the detailed group.
No counting at all still worked
Just setting eating hours: 4.61 kg in 12 months
90 people were split up for 12 months. Those who ate only from 12 pm to 8 pm without counting calories lost 4.61 kg more than those who ate as usual; those who counted and cut calories by 25% lost 5.42 kg more. The two groups did not differ. Both ate 405-425 kcal less a day.
Pooling 23 studies showed the same
A calorie-counting feature didn't change results
An analysis that pooled 23 diet-app studies found app users lost 2.07 kg more at 6 months than people who just waited. But whether the app had a calorie-counting feature did not change how much weight people lost.
Bottom line: counting calories is optional
There are many ways to eat less
People who only set eating hours without counting lost weight with no difference from those who counted. Logging only high-calorie foods made no difference either. And logged numbers were off by as much as 47%. Calorie counting is best seen as one of several tools for eating less.