The ones with modest but real support
A small number of supplements have reasonably consistent, if modest, evidence. Caffeine produces a slight increase in energy expenditure and can support exercise performance and appetite control. Green tea catechins, often paired with caffeine, show small effects on fat oxidation in some studies. Viscous fiber such as glucomannan can increase fullness and modestly reduce intake. None of these is dramatic; the effect sizes are measured in small percentages or pounds, not transformations.
Their benefit is best seen as a minor addition to diet and activity, not a substitute for them.
The ones the evidence does not back
Many heavily marketed products fail to hold up. Garcinia cambogia, raspberry ketones, and conjugated linoleic acid show marginal or inconsistent results in controlled human trials despite bold marketing. The supplement market is loosely regulated, products can be mislabeled or adulterated, and some stimulant-heavy fat burners carry genuine safety concerns.
This is general educational information, not medical advice. Supplements can interact with medications and conditions, so consult a qualified professional and favor regulator-tested products before using any weight-loss supplement.