There are herbal ingredients that have been shown in clinical trials to be effective at starting or accelerating weight loss when compared to a placebo (dummy pills). Unfortunately, many (and maybe most) of the weight loss supplements sold commercially do not contain the proper amounts or forms of these ingredients that were used in the studies and therefore may not be of much value.
Caffeine, Yerba Mate, Guarana seeds, Green tea leaf extract (EGCG) and Cayenne fruit (Capsaicin) have demonstrated positive results in contributing to weight loss by increasing the user’s total daily calorie burn through increasing thermogenesis (increasing metabolism through wasting calories/fat as heat) and by stimulating a desire to increase physical activity through enhanced alertness and stimulation of the central nervous system. Caffeine and caffeine-containing herbs have also demonstrated a positive effect on appetite suppression and fat oxidation (burning). Taken together, these functional ingredients have the potential to produce significant effects on metabolic targets such as satiety, thermogenesis and fat oxidation. These types of supplements are not appropriate for people with adverse reactions to stimulants.
Also, Phase 2®, a proprietary extract of the bean Phaseolus vulgaris, contains phaseolamin, which can block the action of alpha amylase, the enzyme that breaks down carbohydrates and allows them to be absorbed into your body. Five-hundred to 1000 mgs of this natural extract has been shown to reduce the absorption of starches (thus calories) resulting in significantly greater weight loss in studies when compared to placebo. This gives it a potential role as an adjunct weight loss aid, in addition to reducing calories and increasing physical activity.
All the above said, these types of dietary supplements may be appropriate for: 1) people with aggressive goals such as a time limit (e.g. special events on set dates, making a certain weight class for sport or competition, etc.); 2) athletes/entertainers preparing for competition that may require very low body fat; 3) people who have failed multiple times at reaching or maintaining weight goals. The user would stop using the supplement once the weight goal is reached or when they have their daily routines under control to continue making progress without the supplements.