White kidney bean has often been touted as a weight loss aid, and we have to approach these sorts of claims with a bit of skepticism. After all, it seems that there’s a new plant extract every week claiming to be the key to helping people shed pounds. That doesn’t mean that there’s nothing to the science of any of these plant compounds. But, with so many being exaggerated, is white kidney bean actually going to help weight loss?
Well, the short answer is, there is something to the weight loss claims around white kidney beans, but there aren’t a huge amount of studies. We do have a reasonable understanding of how it supposedly works. But, we’d need more studies to be able to say yes it works for sure. There is also the question of how effective it is, and whether or not there are better options for natural weight loss supplements.
So, How Does White Kidney Bean Effect Weight Loss?
The main action is that white kidney bean contains an extract that is what’s known as an amylase inhibitor. That means it has a compound which prevents the body from fully breaking down carbohydrates. It’s a similar mechanism to what is contained in lipase inhibitors that are sometimes prescribed, which helps prevent fat absorption.
And there’s quite a lot of animal studies to show that it works, the problem is that there are only a couple of human studies, and as a result, we aren’t really sure what the effective dose range is, although it does seem to be effective when clinical trials have been done.
The Animal Studies On White Kidney Bean
For example, a study by Song et al.  demonstrated a significant attenuation in weight gain and reduced visceral fat in mice after 98 days of supplementation with 50 mg of extract to kilo of body weight alongside a high-fat diet. Similarly, Micheli et al.  found that mice supplemented with the extract (500 mg per kilo this time) gained significantly less weight compared to the control group after 77 days of consuming a high-fat diet.
There have been further studies which have shown changes to blood work, which showed lower sugar in the blood and with high carb diets. 
The Human Studies on White Kidney Bean
The most cited human study, Birketvedt et al.  conducted a 90 day trial on overweight individuals. They found that those who received the extract experienced greater reductions in body weight, body fat percentage, and waist circumference compared to the placebo group.
This was replicated by Wu et al.  who also found that white kidney bean extract led to significant reductions in waist circumference in the overweight trial participants.
What Dosage of White Kidney Bean Extract Is Best For Weight Loss?
Whilst the exact amount of white kidney bean isn’t well backed, there has been one long term trial (262 days) that compared different dosages. The study did only contain 62 participants , but it gives us some idea when we see that many of the other successful studies used similar amounts at around 750mg per day.
The study in question however considered 300mg 3 times a day to be on the low side for a total of 900mg, with 600mg 3 times a day for a total of 1800mg being the high end. Now, in this trial the high end worked more effectively initially. But, by the end of the trial period the results between the two groups had evened out. Meaning that considering most trials used 750m,  that 750-900mg may be the ideal range for sustained weight loss as the lower supplementation was tolerated better and could easily be fit into 1-2 capsules a day making it more easy to take.
Does White Kidney Bean Extract Work For Losing Weight?
Overall, the evidence from both animal and human studies suggests that white kidney bean could help weight loss. However, further research is needed to fully understand the ideal dosages and if it is comparable to the effectiveness of currently available lipase inhibitors.
1 - https://www.sciencedirect.com/science/article/abs/pii/S1756464615005198?via%3Dihub
2 - https://pubmed.ncbi.nlm.nih.gov/31374931/
3 - https://pubmed.ncbi.nlm.nih.gov/16925860/
4 - Birketvedt, G. Støa, B. Langbakk, and J. Florholmen. "A dietary supplement with bean extract decreases body weight, body fat, waist circumference and blood pressure in overweight and obese subjects." Curr Top Nutraceutical Res 3.2 (2005): 137-142.
5 - Wu, Xiangming, et al. "Enhanced weight loss from a dietary supplement containing standardized Phaseolus vulgaris extract in overweight men and women." Journal of Applied Research 10.2 (2010): 73-80.
6 - https://pubmed.ncbi.nlm.nih.gov/12297207/
7 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7284421/