Diet drinks and sweeteners promise sweetness without calories. Do they help with weight management? A 2017 systematic review in CMAJ reviewed trials and long-term cohort studies.
Trials
The review included 7 randomised trials (1,003 participants, median follow-up 6 months). Non-nutritive sweeteners had no significant effect on BMI (mean difference about -0.37 kg/m2, not statistically significant), and no consistent effects on other body composition measures.
Cohort studies
It also included 30 cohort studies (405,907 participants, median follow-up 10 years). Higher sweetener intake was associated with a modest increase in BMI, plus increases in weight and waist circumference and higher rates of obesity, hypertension, metabolic syndrome, type 2 diabetes and cardiovascular events. These are observational findings, and people who are already gaining weight may choose sweeteners, so they do not prove cause.
The authors’ conclusion
Evidence from trials does not clearly support the intended benefits for weight management, and observational data suggest routine intake may be associated with higher BMI and cardiometabolic risk. Further research is needed.
Practical tips
- Swapping a sugary drink for a zero-calorie one may still cut calories in the short term.
- Do not rely on sweeteners as a weight-loss strategy.
- Water, tea and coffee without sugar are simple alternatives.
Frequently asked questions
Do artificial sweeteners cause weight gain?
Cohort studies found associations with higher BMI, but they cannot prove cause. Trials found no significant effect on BMI.
Do sweeteners help you lose weight?
The trials in the review did not clearly support a weight-management benefit.
Are diet drinks better than sugary drinks?
The review does not compare them directly. Check your overall calories and talk to a dietitian if unsure.
References
- Azad MB et al. (2017). Nonnutritive sweeteners and cardiometabolic health: a systematic review and meta-analysis of randomized controlled trials and prospective cohort studies. CMAJ. PubMed 28716847
General information, not medical advice. Talk to your doctor before changing your diet or having any procedure. Last updated 28 October 2026.
