Do artificial sweeteners help you lose weight?

Short answer

Yes, when they replace sugar. Swapping sugary drinks for zero-calorie ones cut body weight by an extra 1.06 kg, and keeping lost weight off for a year differed by 1.6 kg. Randomized trials did not find that sweeteners raise appetite and cause weight gain.

Do artificial sweeteners help you lose weight?
'Fake sweetness → more appetite → weight gain' — does this formula hold?
Some say zero-calorie sodas and sweeteners help with dieting because they have no calories. Others say the sweet taste triggers appetite and makes you gain weight. We checked trials that randomly assigned people separately from long-term observational studies.
What if you swap sugary drinks for zero-calorie ones?
Body weight fell by an extra 1.06 kg
An analysis that pooled 17 trials and 1,733 people found that those who swapped sugary drinks for sweetened zero-calorie drinks lost 1.06 kg more body weight and 0.6 percentage points more body fat than those who kept drinking sugar. Liver fat also dropped, and no harm was found.
They held up against water too
After 1 year: water 6.1 kg, zero-calorie drinks 7.5 kg
493 people in a 1-year weight-loss program drank either water or sweetened zero-calorie drinks. After 1 year, the water group was 6.1 kg down and the sweetener group 7.5 kg down. Among 220 who carried on alone for another year, it was 3.7 kg vs 4.8 kg at 2 years, with no difference.
They helped keep lost weight off
6 kg more kept off after 1 year
341 people lost weight on a 2-month low-calorie diet, then for 10 months either swapped sweet foods for sweetener products or ate them as usual. After 1 year, the sweetener group kept off 1.6 kg more.
But aren't sweetener users heavier?
Long-term observation and experiments disagreed
Following 405,907 people in 30 studies for about 10 years, sweetener users gained more weight and had more obesity. But in the same analysis, 7 randomized trials (1,003 people) found sweeteners did not raise body mass index. The observational results had reverse causation mixed in: people who are gaining weight choose sweeteners.
Don't they make you eat more?
In trials, people neither ate more nor gained weight
An analysis of randomized human trials found sweeteners did not increase food intake or body weight. In trials lasting 4 weeks to 40 months, people weighed 1.35 kg less than with sugar. The 1.24 kg gap versus water disappeared when a 2024 analysis of 78 trials looked only at high-quality trials, leaving sweeteners equal to water.
Bottom line: replacing sugar helps
The effect is 1-1.6 kg, not large
Swapping sugary drinks or sweet foods for sweeteners meant 1-1.6 kg more weight lost or less regained. Trials did not show sweeteners raising appetite and causing weight gain. Using them in place of sugar works; for someone who already drinks water, the difference is not big enough to switch.