Our results indicate that a test dietary formula containing 445 mg Phase 2 Phaseolus vulgaris
extract taken daily by overweight human subjects concurrently with a carbohydrate-rich portion of a 2000- to 2200-calorie diet is more effective at reducing body weight and body fat mass than placebo. Importantly, the major weight changes are brought about more by fat loss rather than diminution in non-fat body mass as indicated by different means: impedance measurements, waist, hip and thigh measurements, and subcutaneous fat measurements. Earlier, Udani et al. 20
reported reduced body weights and serum triglycerides in 14 obese adults receiving 1500 mg of Phaseolus vulgaris
extract (Phase 2TM
) twice daily with meals for eight weeks. However, values did not reach statistical significance. The clearer statistical differences found in the present study compared to Udani's earlier report where larger doses of extract were used 20
may be due, at least in part, to the care taken to enroll subjects who would comply with a strict protocol.
The purpose of the run-in period was to exclude non-adherent subjects. Obviously, the power to detect a meaningful difference between the active intervention and control groups would be enhanced by removing non-adherent participants. We accept that the ultimately randomized participants will be less representative of the general population of patients. Because the purpose of this trial was to measure efficacy of the agent under study, we chose to measure our parameters under optimal circumstances. Future studies could examine effects under more regular conditions to test the overall effectiveness of the product 26
. Evidence suggesting strong adherence to the present protocol can be gathered from the statistically significant mass losses noted even in the Placebo group relegated to the same caloric-restricted diet as the Test group.
Many published studies concerning methods to combat obesity provide only scale weight loss as the principal end point. The assumption that scale weight loss is synonymous with fat loss, however, is not always true 26,27
. Scale weight decreases may reflect non fat mass loss as much as fat loss. In the present study, indications by many different measurements are that the weight loss is principally due to loss of fat mass. Leg to leg impedance measurements suggest this is true. Although not the “gold standard” like DEXA 26
, perusal of the literature suggests this methodology gives a good first approximation 22-25
. In addition, the use of echograms to estimate subcutaneous adipose tissue and the changes in body circumference in various locations corroborate the conclusions derived from the impedance data.
Further evidence of significant fat loss can be seen in the changes of the calculated body mass index (BMI). BMI is a generally accepted marker of obesity health risk 28
. The lowest health-risk category is among individuals whose BMI's range from 20-25, and the highest risk category is found in individuals whose BMI's exceed 40. A BMI greater than 40, termed as “morbid obesity” or clinically severe obesity, affects more than 15 million Americans. In the test group, BMI was lowered from an initial 25.9±2.0 (SEM) to 24.9±1.9 (SEM) (p<0.001). The placebo group showed no statistical difference from the initial 26.0±2.3 (SEM) to 25.9±2.3 (SEM) (p=0.79). Important to our argument, BMI is known to significantly relate to fat mass – more so than scale weight alone 29
. The marked loss of fat provided in the face of a much lesser changes in non-fat mass caused by the Test formula is exactly what most nutritionists desire.
How do the amylase inhibitors work? Before crossing the intestinal wall, all complex carbohydrates (i.e.,
starches) must be hydrolyzed to their monosaccharide units, in most cases glucose 14
. There are several enzymes involved in this process: a-amylase present in saliva and pancreatic juice, which converts complex carbohydrates into oligosaccharides, and various other enzymes (maltase, lactase, etc.)
present in the brush border of the small intestine that convert these oligosaccharides to monosaccharides that can then be absorbed. Glucose and other monosaccharides generated through this process are transported via
the hepatic portal vein to the liver. Monosaccharides that are not immediately utilized for energy are stored for future energy needs as glycogen in the liver or as fat (triglycerides) in adipose tissue, liver, and plasma 14
We believe the mechanism behind the weight loss relies on the reported a-amylase-inhibiting activity of the Phaseolus vulgaris
. Phaseolus vulgaris
extract has been shown in vitro
to inhibit the activity of a-amylase and may help promote weight loss by interfering with the digestion of complex carbohydrates to simple, absorbable sugars, potentially reducing carbohydrate-derived calories 30,31
. Also, slowing of the rapid absorption of carbohydrates would favorably influence the insulin system that could, in turn, lead to lesser fat accumulation 27
. We have previously shown in a rat model the ability of so-called “carbohydrate blockers” to prevent early absorption of rice starch and sucrose and prevent insulin resistance 32
There is yet another mechanism that could contribute to the weight loss. Some dietary carbohydrates have a physical form that makes them inaccessible to a-amylase and, therefore, resistant to digestion in the human gastrointestinal tract. These resistant starches enter the colon
largely undigested, where they are fermented by colonic bacteria to produce short-chain fatty acids, carbon dioxide, and methane. Resistant starches yield approximately 50 to 80% of the energy obtained from glucose, the principal product of non-resistant starch digestion 14
. It has been reported that resistant starch consumption promotes lipid oxidation 21
. Suffice it to say, starch blockers send starch to distal digestive sites where they may have effects similar to the resistant starches 21
Although the active formula used in the present investigation consisted of many ingredients, we believe virtually all of the effect on body fat loss derived from the bean extract in the preparation. If one peruses the list of other ingredients, it is apparent that only the chromium picolinate could be involved in any significant fat loss 33
. Nevertheless, the amount of chromium picolinate (0.5 mg/tablet) present in the bean extract-containing formula should have had little influence on body composition due to the small dosing. The amount of elemental chromium in 0.5 mg of chromium picolinate would amount to roughly 50-60 mcg supplementation per day. Changes in body composition measures following chromium picolinate use have been seen sporadically in some studies, but generally only at dose levels of 200 mcg Cr or greater 33-37
. Based on a review of several published human studies, Vincent 38
concluded that chromium picolinate supplementation has relatively little effect on body composition even if an exercise program is involved when given at larger daily doses than in the present study.
Raw Phaseolus vulgaris
beans contain a variety of potentially toxic substances. In animals, reduced food intake, impaired weight gain, and even deaths have been noted. 39,40
. In humans, consumption of raw or undercooked kidney beans has been associated with transient, often severe gastrointestinal disturbances 41,42
. These effects have been largely attributed to phytohemagglutinens (PHA) present at high levels in raw beans. However, two facts are important here. PHA levels can be reduced considerably by cooking, and small white navy beans are reported to have negligible levels compared to colored beans, which possess high levels of PHA's. Suffice it to say, the extract used in our study (Phase 2TM
) is a standardized white kidney bean extract prepared using heated processing conditions to substantially inactivate hemagglutinating activity (HA) and trypsin inhibiting activity (TIA) while preserving alpha-amylase inhibiting ability. The established product is standardized to contain less than 3,400 HA units per gram and less than 40 TIA units per mg dry weight.