Benefits
Weight and fat loss
In a 12-week, double-blind, placebo-controlled trial in 81 adults with overweight or moderate obesity, everyone was on a reduced-calorie diet and the group taking 1000 mg three times daily lost 4.5 kg against 0.5 kg on placebo, and 3.2 kg of fat mass against 0.7 kg. The 700 mg group lost 3.2 kg, but its fat-mass change was not significantly different from placebo. Pooled across eight trials the average gap is smaller, about 1.6 kg.
Carbohydrate blocking
By inhibiting starch-digesting enzymes, the extract is meant to reduce the sugar and calories absorbed from starchy foods. The cited trial measured body weight and fat, not the calories actually absorbed, so this is the proposed mechanism rather than a measured result.
Unproven blood sugar effect
The mechanism suggests this, but the human evidence does not back it. A glycemic index study of the same extract found no significant effect from capsules, only from a 3 gram powder dose, and in the 12-week trial HbA1c, cholesterol, LDL and HDL did not differ from placebo.
Mechanism of action
Alpha-amylase inhibition
Phaseolamin binds and temporarily inactivates alpha-amylase, slowing the breakdown of starch into absorbable sugars.
Reduced caloric absorption
With less starch digested in the small intestine, some passes onward undigested, lowering the meal's effective calorie load.
Clinical trials
12-week, double-blind, placebo-controlled randomized trial with three arms: Phase 2 at 1000 mg, Phase 2 at 700 mg, or a cellulose placebo, each taken three times a day 30 minutes before meals while all participants followed a reduced-calorie diet. Sponsored by InQpharm and financially supported by Pharmachem and others, and two of the authors are consultants to Ashland, the manufacturer of Phase 2. (Jäger et al. 2024, Scientific Reports)
81 adults with overweight or moderate obesity, BMI 25 to 34.9, completed the trial out of 90 randomized, split 36 on the high dose, 18 on the low dose and 36 on placebo. All followed a diet cut by about 20 percent of their calculated energy needs, and calorie intake and activity did not differ between the groups. 12 weeks.
The 1000 mg dose reduced body weight by 4.5 kg versus 0.5 kg on placebo, fat mass by 3.2 kg versus 0.7 kg, BMI by 1.6 versus 0.2, and waist by 3.9 cm versus 1.0 cm. The 700 mg dose lost 3.2 kg of body weight, but its fat-mass change did not separate from placebo. Cholesterol, LDL, HDL and HbA1c did not differ between groups. Adverse events were similar across groups; one serious event, a pulmonary embolism in the 700 mg group, was judged unlikely to be related to the supplement.