No one doubts that obesity is a problem in the United States. According to figures released by the Centers for Disease Control (CDC) in January 2010 analyzing the period 2007–2008, the prevalence of obesity was 32.2 percent among adult men and 35.5 percent among adult women. The age-adjusted prevalence of overweight and obesity combined was 68.0 percent overall; 72.3 percent among men, and 64.1 percent among women. That’s right: in 2008 an estimated 68 percent of Americans were overweight or obese! To put this in perspective, from 1960–2 to 2005–6, the prevalence of obesity increased from 13.4 to 35.1 percent in U.S. adults 20 to 74.7 years of age. Statistics for those overweight were in the same range. Within living memory, the proportion of Americans who are overweight and obese has more than doubled. Quite obviously, there has been no massive shift in genetics in the U.S. in the last 50 years, so what has caused such weight gain?

In his book, Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control and Disease, Gary Taubes points out that under real life conditions, prior to the advent of refined carbohydrates, human beings appear to have suffered from no chronic diseases that can be linked directly to the consumption of fats. Apparently, eating fat does not make us fat. Among his ten “inescapable” conclusions (p. 454) is this. “Dietary fat, whether saturated or not, is not a cause of obesity, heart disease, or any other chronic disease of civilization…“ (Taubes is a contributing correspondent for Science magazine and a contributing editor at Technology Review.)

In contrast, Taubes documents the thesis that with the advent of the age of refined carbohydrates, built-in mechanisms for regulating appetite, on the one hand, and regulating energy use, on the other hand, have become dysfunctional. Sucrose and high-fructose corn syrup are particularly harmful to metabolic regulation. Evidence from Taubes and others shows over the last 100 years, consumption of simple, refined and processed carbohydrates has increased between 50 – 60 percent. Some authorities estimate that perhaps 15 percent of the calories in the American diet now come from fructose alone!

To the fundamental question of what regulates fat accumulation, which is to say, weight gain, Taubes answers simply. “This was elucidated by 1965 and has never been controversial. Insulin is the principle regulator of fat metabolism...”


Let’s start with evidence from diet trials. Low carbohydrate versus low fat diets for the most part boils down to low insulin versus high insulin diets. Large comparative trials have demonstrated convincingly high protein and Atkins-style diets can be used quite successfully for weight loss and weight maintenance. Moreover, low carbohydrate diets are more successful than low fat diets in terms of delivering health benefits unless there is very careful attention in the carbohydrate-based diets to what is termed the “glycemic load.” After several decades of refusals in medical circles even to test the low carbohydrate diet hypothesis, the tide may be turning. Researchers conducting a recent trial concluded, “Reducing glycemic load may be especially important to achieve weight loss among individuals with high insulin secretion...”

Other researchers were more direct after a short-term trial of diabetics on a very low carbohydrate diet. “When we took away the carbohydrates, the patients spontaneously reduced their daily energy consumption by 1,000 calories a day. Although they could have, they did not compensate by eating more proteins and fats and they weren’t bored with the food choices.”

Put differently, even if it remains subject to debate as to which is more responsible for the current epidemic of obesity — fat or carbohydrates in the diet — it has become indisputable that insulin makes us fat and carbohydrate consumption powerfully influences insulin levels.

High blood insulin levels after meals decrease the ability to access fuels, especially fats, for energy for several hours, leading to hunger and overeating as well as reducing natural increases in caloric expenditure. For instance, the thermic response to food that should account for a full 10 percent of all calories metabolized during the day is blunted in the overweight. Low-glycemic load foods include non-starchy vegetables, legumes, and temperate fruits in contrast to high-glycemic load foods, such as refined grains, starchy vegetables, fruit juices and sweets. The former cause only small fluctuations in serum insulin levels whereas the latter can cause large swings. A low-glycemic diet by reducing insulin fluctuations not only reduces hunger, weight gain and belly fat storage, but also reduces triglyceride levels while improving the levels of “good” high-density lipoprotein cholesterol (HDL). This hypothesis has been borne out by a study lasting six years. The highest insulin secretors exhibited the largest change in weight and belly fat compared to the lowest insulin secretors. Those who were high insulin secretors and ate low-fat diets did even worse.


Insulin controls blood sugar clearance—and a lot more. Testing blood sugar levels and even glucose tolerance is easy and inexpensive, whereas testing insulin levels, and especially testing insulin sensitivity, is time consuming and costly. Not surprisingly, the medical world largely has shunned insulin testing and often pretends other tests can be substituted. Such attitudes have limited some important research. One of those areas is the impact of directly reducing insulin levels—not blood glucose levels!—on weight loss.

Such an experiment was performed more than a dozen years ago with remarkable results. Researchers reasoned that hyperinsulinemia is a possible preceding event in the development of obesity. Rather than treating blood glucose levels, they reduced insulin levels with a pharmaceutical inhibitor of insulin secretion called diazoxide. In a double-blind placebo-controlled clinical trial with hyperinsulinemic obese adults lasting eight weeks and utilizing a low calorie diet, it was determined that reducing insulin output increased weight loss significantly without causing hyperglycemia.

This was not a fluke finding. A clinical trial conducted at a hospital in the Netherlands and published in 2008 reduced insulin levels through diazoxide treatment while prescribing moderate caloric restriction. Researchers expected a 15 percent drop in starting body weight after six months. (Even ten percent is considered a great success.) They were not disappointed. Body weight decreased by almost 21 pounds, total body fat mass decreased by 23.3 percent and yet there was no loss of lean body mass or bone mass. Fat loss was inversely related to fasting insulin levels achieved at six months—the lower the insulin, the greater the fat loss. Diastolic blood pressure (the bottom figure) decreased by 10.9 mmHg. Fasting and post-meal peak insulin levels were reduced by about 65 percent, which is to say, they decreased to the normal range for non-obese men. Haemoglobin A1c (glycosolated haemoglobin, an indicator of blood glucose control) increased slightly by 0.5 percent to 5.9 +/- 0.2 percent, which is still within the normal range. The weight loss was judged to be clinically significant.

Reducing insulin levels without any attempt to reduce blood sugar levels powerfully affects both appetite and weight regulation. Why. As mentioned earlier, elevated insulin levels seriously interfere with normal metabolism and reduce the ability to take fat out of storage and use it for energy. Something similar happens with appetite. In those who are overweight, the signal to the brain from the meal-induced release of insulin often is disrupted, making it more difficult for the brain to register that sufficient calories have been ingested for same-meal satiety. One result is over-eating. Insulin resistance actually causes a change in the microcirculation between the body and the brain. Other results are uneven energy levels, increased between-meal snacking and binge eating.


Has the reader ever seen a dietary supplement marketed for reducing insulin levels. Probably not. There are many natural products marketed for supporting blood glucose regulation, but insulin regulation is another story. Indeed, many products sold for blood glucose control work by increasing insulin levels in order to reduce blood glucose levels. However, elevated serum insulin is the fundamental driver for Syndrome X / the Metabolic Syndrome. Increasing natural insulin output in diabetics who have lost the ability to produce normal amounts of insulin may be beneficial, but doing so in non-diabetics and in those who already produce too much insulin is another matter.

An example of this is the popular herb Gymnema sylvestre. G. sylvestre does not reduce insulin resistance, but rather increases insulin output. It also reduces the absorption of ingested fats, an action that may appear to be beneficial until one considers the implications for nutrients such as vitamins A, D, E, K, CoQ10, tocotrienols, omega-3 fatty acids, etc. There is some evidence that extracts of G. sylvestre may improve the functioning of insulin-producing beta-cells in the pancreas, which can be a good thing in some diabetics. On a less positive note, there also is evidence G. sylvestre, most likely by elevating blood insulin levels, can raise blood pressure.

Fortunately, there is at least one natural item that has been shown to reduce insulin levels as well as reduce both hunger and weight gain. That item is known colloquially as Assam Gelugur.


“Assam” means “sour.” Assam Gelugur (variously spelled) is a Southeast Asian name for a family of very sour fruits used for flavoring, in cooking, preserving and as herbal medicine. One local use is for weight loss. In Thailand and throughout the Malay Peninsula, the primary species is Garcinia atroviridis. Related species used for much the same purposes are G. cambogia and G. indica. The active constituent in the fruit is its acid, which has the formidable chemical name 1,2-dihydroxypropane-1,2,3-tricarboxylic acid.

As is true of many herbal products, the benefits of Assam Gelugur extracts are highly dependent upon how they are prepared. The acid must be stabilized generally by the addition of high pH ions (basic or alkali), such as those of potassium, magnesium or calcium — using the wrong stabilizer results in little or no activity. Employing only potassium as the cation, if the material is properly reacted, results in a liquid, not a powder, hence leads to a product that is commercially unusable. In the case of the acid derived from Assam Gelugur, adding any calcium at all reduces some desired benefits and blocks other benefits entirely.

At the 2005 Annual Meeting of the American College of Nutrition, for the first time it was reported that a proprietary potassium-magnesium salt of the Assam Gelugur acid in an animal model gave the same blood glucose regulation as found in the control arm of the test while almost literally cutting insulin levels in half ! The same study demonstrated this salt dramatically improved glucose clearance from the blood, lowered systolic blood pressure and also lowered several key indicators of inflammation, including C-reactive protein and tumor necrosis factor-alpha (TNF-alpha). In contrast, the potassium-calcium salt exerted no effect upon insulin and blood sugar regulation and only very poorly influenced blood pressure. In the areas of insulin metabolism, glucose regulation and blood pressure, the proprietary potassium-magnesium salt was between five and ten times as active as the potassium-calcium salt of the fruit acid.

Extracts of Assam Gelugur in clinical trials repeatedly have shown to be safe and to improve weight loss and appetite control. The new wrinkle is the discovery of the proper technique for producing a stable extract that dramatically reduces insulin levels while at the same time improving blood glucose regulation. The validity of this material (a combination of proper extract plus unique delivery system), which is marketed under the name Leptisol®, soon will be explored decisively at a major university. This particular extract and delivery of Assam Gelugur has been chosen by the National Institutes of Health for a National Center for Complementary and Alternative Medicine clinical trial expected to begin at the end of the year.

Modern diets typically contain refined carbohydrates, especially sugars. These diets increase the storage of consumed fats and other calories while at the same time preventing the utilization of stored and consumed fats for energy. The mechanism involved is an elevated release of insulin, which leads to lessened meal satiety, poor regulation of appetite and weight gain. The solution. Low-glycemic load foods (remember, vegetables can be your primary sources of carbohydrates in place of bread, rice, etc.), higher protein consumption (not necessarily all from animal sources) and, perhaps, an extract from an Asian fruit called Assam Gelugur.

Dallas Clouatre, PhD

Dallas Clouatre, Ph.D. earned his A.B. from Stanford and his Ph.D. from the University of California at Berkeley. A Fellow of the American College of Nutrition, he is a prominent industry consultant in the US, Europe, and Asia, and is a sought-after speaker and spokesperson. He is the author of numerous books. Recent publications include "Tocotrienols in Vitamin E: Hype or Science?" and "Vitamin E – Natural vs. Synthetic" in Tocotrienols: Vitamin E Beyond Tocopherols (2008), "Grape Seed Extract" in the Encyclopedia Of Dietary Supplements (2005), "Kava Kava: Examining New Reports of Toxicity" in Toxicology Letters (2004) and Anti-Fat Nutrients (4th edition).


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