Do women lose less weight than men?

Short answer

By the scale, slightly less. On the same diet men lost 11.8% and women 10.3%, because men's bigger bodies burn more calories a day. When exercise calories were matched, there was no difference between men and women.

Do women lose less weight than men?
'Women have a slower metabolism, so they lose less doing the same thing' — true?
It is common to hear that when a couple starts a diet together, the man loses weight faster and more. Does that mean women's bodies just don't lose weight well? We checked trials that reported results for men and women separately.
On the same diet, men lost a bit more
In 8 weeks: men 11.8%, women 10.3%
2,224 people (1,504 women, 720 men) ate an 810 kcal-a-day diet for 8 weeks. Men lost 11.8% of their body weight and women 10.3%. Improvement in blood sugar control did not differ between men and women.
The reason was body size
The same 810 kcal is a bigger shortfall for men
In this study men averaged 109.4 kg and women 95.6 kg. By the researchers' estimate, men needed about 3,086 kcal a day and women about 2,353 kcal. Eating the same 810 kcal leaves a daily shortfall of about 2,276 kcal for men and 1,543 kcal for women, so men's is bigger.
The early gap was not just fat
In 2 months men lost twice the weight and 3 times the lean mass
287 people (210 women, 77 men) dieted for 6 months. In the first 2 months men lost twice as much weight as women, and three times as much lean mass (muscle and everything except fat). Between months 2 and 6, the non-fat share of weight lost became similar: 7% in men and 5% in women.
What if exercise calories are matched?
The gap between men and women disappeared
In a 16-month exercise trial, men lost 5.2 kg while women's weight stayed the same. Exercise was set by time, so heavier men burned more calories. When 141 people were set to burn 400 or 600 kcal per session for 10 months, men in the 400 kcal group lost 3.8 kg and women 4.1 kg, with no difference between men and women.
Over a year or more
Even when men come out ahead, the gap is under 1 kg
An analysis pooling 13 trials lasting a year or more found no difference between men and women in weight lost, in kg or in percent. An analysis of 5,531 people found the 12-month program effect was 2.58 kg for men and 1.71 kg for women, a 0.87 kg gap. Even in studies where men lost more, women also lost a clear amount.
Women's bodies are not resistant to weight loss
On weight-loss injections, women lost 1.04 kg more
An analysis pooling 14 trials of weight-loss injections (the GLP-1 type) found women lost 1.04 kg more than men, or 1.69 percentage points more. The bigger the weight loss, the bigger this gap. That could not happen if women's bodies were simply built to lose less.
Bottom line: losing less comes down to body size
Women can judge progress by their own calories, not men's numbers
Men lost more on the same diet because their bigger bodies created a bigger daily calorie shortfall. When exercise calories were matched there was no difference, and over a year or more the gap was under 1 kg. Women can skip comparing kg with men and look at the share of their own body weight lost instead.