After the FDA banned a popular weight-loss supplement ephedra, many people assumed that finally, after hundreds of cases of dizziness and heart palpitations, the safety issue had been laid to rest. Not so fast, says Dr. Tod Cooperman, of the independent research firm consumerlab.com.

Caffeine: weight loss Recent testing by Cooperman suggests that some manufacturers have just jacked up a new generation of “safe” supplements with caffeine. Lots of caffeine. His tests found that the maximum daily dose of Ripped Fuel, for example, had 581 mg of caffeine, roughly equal to a 12-pack of diet cola.

The daily max of another popular ephedra-free product, Zantrex-3, contained the equivalent of two 12-packs. Ripped Fuel’s manufacturer has disputed the scientific basis of Cooperman’s findings, while the maker of Zantrex-3 points out that users can regulate intake by limiting their doses.

The problem is, intake can be hard to gauge because the labels often list straight caffeine separately from things like guarana, green tea, yerba mate, and kola nut – all sources of caffeine. Whatever it’s called, mixing high levels of caffeine with exercise can be dicey, particularly for those with heart risk factors.

Caffeine can further raise blood pressure already elevated during exercise. And in rare cases, mega caffeine amounts can disrupt the heart’s rhythm. Also of concern is the ingredient Citrus aurantium, or bitter orange. Sort of a weaker version of ephedra, it’s generally considered safe when taken alone – but it tends to have a multiplier effect when taken with caffeine.

Caffeine weight loss: safety To stay safe, stay away from weight loss supplements that are overloaded with caffeine, or better yet, ditch weight loss pills altogether. If you do take them, make sure you know how much caffeine one serving contains. If you want to try bitter orange, buy a decaf product like Solaray and get your caffeine from a predictable source, like coffee. [via]