Benefits
Weight and fat loss
In a 12-week placebo-controlled trial in 81 adults with overweight or moderate obesity on a reduced-calorie diet, 1000 mg three times daily was followed by 4.5 kg weight loss versus 0.5 kg on placebo, and 3.2 kg less fat versus 0.7 kg. An earlier 8-week trial in 27 completers found no statistically significant difference, and pooled analyses range from a non-significant result to an average gap of about 1 to 1.6 kg.
Starch-digesting enzyme inhibition
When a partially purified white bean inhibitor was infused directly into the human duodenum, it blocked more than 94 percent of amylase activity. Swallowed starch blocker tablets from the 1980s, however, did not change how many calories passed into the stool after a starchy meal. No study has measured how much starch Phase 2 itself keeps from being absorbed.
Blood sugar response to white bread
In an open-label crossover study in 13 people, Phase 2 capsules of 1500 to 3000 mg taken with white bread did not significantly lower its glycemic index; only the 3000 mg powder did, by about 34 percent. In the 12-week weight trial HbA1c did not differ from placebo, and a pooled analysis of bean extract trials found no change in fasting glucose.
Mechanism of action
Alpha-amylase inhibition
Phaseolamin, the amylase inhibitor in white beans, inactivates alpha-amylase and so slows the breakdown of starch into absorbable sugars. A partially purified white bean inhibitor infused into the human duodenum inactivated more than 94 percent of amylase activity, and the researchers judged that earlier commercial products failed mainly because they had too little inhibitor activity.
Proposed reduction in starch absorption
The proposed result is that some starch passes through the small intestine undigested, lowering a meal's usable calories. This has not been measured for Phase 2, and older commercial starch blocker tablets did not increase the calories lost in the stool.
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)
90 adults with overweight or moderate obesity (BMI 25 to 34.9) were randomized, 36 to the high dose, 18 to the low dose and 36 to placebo, and 81 were included in the final analysis. 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. Fat-free mass also fell more on both doses than on placebo, by 1.4 kg on the high dose. 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.
Randomized, double-blind, placebo-controlled trial of 1500 mg Phase 2 or an identical placebo twice daily with meals for 8 weeks. (Udani et al. 2004, Altern Med Rev)
Obese adults: 50 were screened, 39 passed screening and 27 completed the 8 weeks.
Weight loss did not differ significantly: 3.79 lb (about 1.7 kg) on Phase 2 versus 1.65 lb (about 0.75 kg) on placebo (p = 0.35). Triglycerides fell 26.3 mg/dL versus 8.2 mg/dL, also not significant (p = 0.07). No adverse events were attributed to the product.
Open-label, 6-arm crossover study testing white bread with and without Phase 2 in capsule and powder form at 1500, 2000 and 3000 mg, using standardized glycemic index testing. (Udani et al. 2009, Nutr J)
13 randomized participants given single test meals; no long-term supplementation.
Capsules had no significant effect at any dose: the 1500 mg dose had no effect, and 2000 and 3000 mg gave non-significant reductions. Only the 3000 mg powder significantly lowered the glycemic index of the bread, by about 34 percent (p = 0.023). The comparisons were not adjusted for multiple testing.