As of April 2015, no human studies have proven the effectiveness of raspberry ketones in aiding weight loss, reports Authority Nutrition. Some studies of Garcinia Cambogia show a small increase in weight loss, while many indicate the supplement has no effect at all.
A single human study included raspberry ketones in a mixture of other supplements as part of a treatment, reports Authority Nutrition. This eight-week study found a 7-percent drop in fat tissue in the treated group, as compared to only a 2-percent drop by the placebo group. This difference could be the result of other substances included in the treatment, including caffeine, garlic and ginger. A study using rats determined that raspberry ketones aid in fat loss, but the doses used on the rats were higher than what is practical for everyday human supplementation.
A study of 135 overweight individuals found that Garcinia Cambogia actually reduced the amount of weight lost when compared to a placebo, according to Authority Nutrition. This difference was small enough to be deemed statistically insignificant, however. Other studies show a modest improvement in fat loss with the supplements: A study of 89 obese women found Garcinia Cambogia led to 2.8 additional pounds lost over 12 weeks. A review article in the Journal of Obesity in 2011 states that the supplement may boost weight loss by about 2 pounds over a few weeks.