Do weight loss pills work? There isn't overwhelming evidence that any dietary supplement enables significant, long-term weight loss. However, many small studies — typically funded by supplement companies -- suggest short-term weight loss, slimming (reducing fat but not overall weight), and/or appetite reduction (see What It Does for a summary of the evidence).
In this Review, CL focused on stimulant blends (which are some of the most popular weight loss supplements and contain caffeine and/or synephrine), as well as supplements with 7-keto DHEA or forskolin (from Coleus forskohlii). CL has separately reviewed many other types of supplements used for weight loss — see the list in What It Is.
What did CL's tests of weight loss supplements find? Laboratory tests and analyses by ConsumerLab revealed potentially dangerous amounts of caffeine in three products and a potentially dangerous amount of synephrine in another — twice the amount expected from its label. In addition, one Forskohlii supplement contained less than 5% of its expected forskolin. All of the 7-keto DHEA supplements contained their claimed amounts.
Across products, the dose of caffeine ranged from 51.6 mg to 270 mg per serving in stimulant blends, 7-keto DHEA ranged from 25 mg to 100 mg, and forskolin ranged from just 1.9 mg to 50 mg. The cost to obtain 100 mg of 7-keto DHEA ranged from 15 cents to $3.00 and the cost for 25 mg of forskolin ranged from 33 cents to $1.40 -- showing huge opportunity for savings when buying these products. For details, see What CL Found.
- Top Picks for 7-Keto DHEA, forskolin, and stimulant blends — Among products Approved in testing, ConsumerLab selected a Top Pick for 7-Keto DHEA and a Top Pick for Forskolin, with each providing the clinically tested dosage at relatively low cost. A Top Pick Stimulant Blend was also chosen that provided a safe level of caffeine.
- How much should I take and when? Dosage for 7-Keto DHEA is typically 100 mg twice daily and for Forskohlii it is 25 mg of forskolin (from 250 mg of extract standardized to 10% forskolin) twice daily. For caffeine, there isn't sufficient research to suggest a dose effective for weight loss. See the ConsumerTips™ section for more about dosage and forms.
- Safety and side effects of weight loss supplements: Stimulants and forskolin may affect blood pressure and heart rate and interact with medications. 7-keto DHEA may affect thyroid levels. (For details, see Concerns and Cautions.)