The claim that coffee helps you lose weight is partially supported but usually exaggerated. The caffeine in coffee can sometimes temporarily increase metabolism and suppress appetites. However, these effects are very short term, and coffee by itself does not lead to any meaningful and sustained weight loss for most people.
https://pubmed.ncbi.nlm.nih.gov/30335479/ This review and meta-analysis of 13 randomized controlled trials found that higher caffeine intake was associated with modest reductions in body weight. However, the studies showed high variability, which suggests that while caffeine has the possibility of contributing to weight reductions, the effects are inconsistent.
https://www.scientificamerican.com/article/can-coffee-cause-weight-loss-by-affecting-appetite-and-digestion/ This secondary source(2024) analyzes different studies and breaks the information down into an easy to comprehend article for the public to read. The article agrees with my other source, and Frank Hu, a chair of the department of nutrition at Harvard, advises against "unrealistic expectations that drinking a lot of coffee will dramatically change your body weight."
My primary source would not have any biases and is only searching for accurate information. My secondary source could be biased towards people who believe coffee can lead to weight loss in order to entice viewers, but the conclusion of that source suggests that it doesn't lean heavily into that bias.
One piece of evidence that supports this claim is that caffeine has been shown to increase thermogenesis, which raises the number of calories the body burns during rest. Also, coffee is low in calories, so if you're drinking coffee as a replacement to high-calorie beverages, that would lead to a decrease in body-weight.
The metabolic appetite-suppressing effects of caffeine tend to diminish as people increase their tolerance, which undermines the claim in the long term. Also, many coffee drinks contain added sugars and creams, which can significantly increase calorie intake and contribute to weight gain rather than loss.