~ What Makes People Fat, Why Diets Don't Work, and What Triggers Appetite?

From Dr. Michael T. Murray's Natural Facts Newsletter. Reprinted with permission.


There is no denying it; obesity is now a major epidemic in the United States. In response, researchers have been diligently seeking the answer three important questions - What makes people fat, why diets don't work, and what triggers appetite?

The answer to the first question can be answered simplistically. Obesity is simply the result of eating more calories than are being burned by the body. However, it is much more complex of an issue than that. In fact, what modern research has uncovered is that obesity is not just a matter of overeating. There are sound physiological reasons why some people can eat very large quantities of calories and not increase their weight substantially while for others just the reverse is true. It is beyond the scope of this article to go into great detail, so I will limit the discussion to taking a look at some of the interesting aspects of why some people are prone to obesity and how to effectively promote weight loss by improving insulin sensitivity and impacting appetite regulating compounds.

In the beginning

Although there may or may not be a specific "obesity gene," the tendency to be overweight is definitely inherited. Also important in determining the likelihood of developing obesity during pregnancy. An excess of calories during this stage of development can lead to the formation of an increased number of fat cells - hyperplastic obesity While hyperplastic obesity tends to be associated with fewer serious health effects compared to hypertrophic obesity, it is still linked to diabetes, heart disease, high blood pressure, and other serious disturbances of metabolism. Usually with hypertrophic obesity the fat distribution is generally around the waist with a greater waist to hip circumference.

The "set point" theory

Research with animals and humans has found that each person has a programmed "set point" weight. The "set point" is the weight that a body tries to maintain by regulating caloric intake. It has been postulated that individual fat cells control this set point: when the fat cell becomes smaller, it sends a powerful message to the brain to eat. Since the obese individual often has both more and larger fat cells, the result is an overpowering urge to eat.

The existence of this set point explains why most diets don't work. While the obese individual can fight off the impulse to eat for a time, eventually the signal becomes too strong to ignore. The result is rebound overeating with individuals often exceeding their previous weight. In addition, their set point is now set at a higher level making it even more difficult to lose weight. This effect has been termed the "ratchet effect" and "yo-yo dieting."

The set point seems to be tied to how sensitive the fat cells are to insulin. It is well established that obesity leads to insulin insensitivity and vice versa. When fat cells, particularly those around the abdomen, become full of fat they secrete a number of biological products (e.g., resistin, leptin, tumor necrosis factor , free fatty acids) that dampen the effect of insulin, impair glucose utilization in skeletal muscle, and promote glucose production by the liver. Also important is that as the number and size of fat cells increase it leads to a reduction in the secretion of compounds that promote insulin action including a novel protein produced by fat cells known as adiponectin.

Adiponectin not only is associated with improved insulin sensitivity, it also has anti-inflammatory activity, lowers triglycerides, and blocks the development of atherosclerosis (hardening of the arteries). The net effect of all of these actions by fat cells is that they severely stress blood sugar control mechanisms as well as lead to the development of the major complication of diabetes - atherosclerosis. Because of all of these newly discovered hormones secreted by fat cells, many experts now consider the adipose tissue a member of the endocrine system.1-3

Diet-induced thermogenesis

Another physiological difference between obese and thin people is how much of the food consumed is converted immediately to heat. This process is known as diet-induced thermogenesis (heat production). Researchers have found that in lean individuals a meal may stimulate up to a 40% increase in diet-induced thermogenesis. In contrast, overweight individuals often display only a 10% or less increase.4 In overweight individuals the food energy is stored instead of being converted to heat like it is in lean individuals.

Just like in a fat cell's set point, a major factor for the decreased thermogenesis in overweight people is insulin insensitivity.5 Therefore, once again the goal is to enhance insulin sensitivity.

Key triggers of an increased appetite

It could be argued that obese individuals are more sensitive to internal signals to eat along with being extremely susceptible to external stimuli (sight, smell, and taste) that can increase the appetite. Psychological factors undoubtedly play a role in why many people overeat, but the bottom line is that if we can quell the physiological triggers most people can overcome their appetite, cravings, or food addictions.

Appetite reflects a very complex system that has evolved to help humans deal with food shortages. As a result it is extremely biased towards weight gain. It makes sense that people who survived famines were those that were more adept at storing fat than burning it. So, there is a built in tendency for all of us to overeat even though in developed countries food is readily available.

To combat the tendency to eat more than we require, we must accentuate the normal physiological processes that curb the appetite. A very elaborate system exists that is supposed to tell the hypothalamus when the body requires more food as well as when enough food has been consumed. Most of the stronger signals actually originate from the gastrointestinal tract. In addition to nerve signals feeding back to the CNS, there is a growing list of gut-derived hormones and peptides such as neuropeptide Y and analogs, ghrelin, and cholecystokinin. Undoubtedly, you have heard of the promising research on at least some of these compounds.

For example, last September the New England Journal of Medicine reported peptide YY 3-36 (or PYY for short) dramatically reduced appetite in both obese and normal weight individuals.6 The subjects consumed about 30 % less at an all you can eat buffet after the infused hormone, compared with when they were given only saline solution. The subjects also ate significantly less over the next 24 hours.

Unlike PYY, the stomach-derived hormone Ghrelin increases appetite. Ghrelin levels are highest when the stomach is empty and during calorie restriction. Obese individuals tend to have elevated ghrelin levels, when they try to lose weight ghrelin levels increase even higher. Part of the success of gastroplasty in producing permanent weight loss is thought to be the result of significantly reduced ghrelin levels. For example, while a diet-induced weight loss of 17 % of initial body weight was associated with a 24% increase in the area under the curve (AUC) for the 24-hour ghrelin profile, despite a 36% weight loss after gastric bypass, the AUC for the ghrelin profile in the gastric-bypass group was 77 % lower than in normal-weight controls and 72 % lower than in matched obese controls.7

While using various appetite regulators as therapeutic agents in human obesity is possible, preliminary studies seem to indicate that in humans compensatory actions may negate the effect. The perfect drug or natural product to impact appetite must possess an ability to increase insulin sensitivity and to produce a targeted effect of reducing those factors which increase appetite while simultaneously increasing those factors that decrease appetite. I believe that part of the answer in helping people lose weight safely, effectively, and permanently is PGX - a unique blend of selected, highly viscous soluble fibers that act synergistically to develop a higher level of viscosity and expansion with water than with the same quantity of any other fiber alone.

Utilizing PGX to improve insulin sensitivity and control appetite The development of PGX began as a solution to obesity, diabetes, and heart disease began with intense scientific research at the University of Toronto. What Dr. Vuksan and his colleagues discovered was that by combining various soluble fibers in specific ratios, the viscosity of the fiber is amplified greatly. This enhanced viscosity is paramount to its effects, as the viscosity of soluble fiber is directly related to its physiological effects and ultimately its overall health benefits in humans.

Beginning in 2002, Michael Lyon, M.D., of the Canadian Center for Functional Medicine began working cooperatively with the University of Toronto researchers, modifying their formulation for better stability through the digestive tract and improving upon its characteristics as a food ingredient. Through Dr. Lyon's work significant improvements were made. For example, the fiber blend in PGX was improved so that it has a modest viscosity when first mixed, but the viscosity increases greatly once it reaches the stomach and intestine. This makes PGX easy to mix in the blender, but once it hits the stomach it forms a very large gelatinous mass. The viscosity and physical properties of PGX make it completely unique amongst all other water soluble fibers and fiber blends. Its appetite suppressing and blood sugar stabilizing properties continue for hours after each administration.

Clinical studies conducted by Dr. Vuksan and his colleagues have repeatedly shown that after-meal blood sugar levels decrease as soluble fiber viscosity increases.8-10 As a result, PGX produces benefit unlike any other fiber source. This relationship with viscosity has also been shown to hold true for the other physiological benefits produced by soluble fibers including increased insulin sensitivity, diminished appetite, significant weight control, improved bowel movements, and decreased serum cholesterol.

PGX lowers after meal blood sugar levels by approximately 20 to 40% and also lowers insulin secretion by approximately 40% producing a whole body insulin sensitivity index improvement of nearly 50% - a phenomenal accomplishment that is unequalled by any drug or natural health product.10 PGX is particularly well-suited for syndrome X - a collection of metabolic abnormalities including impaired glucose tolerance, high blood cholesterol and triglyceride levels, high blood pressure, and upper body (abdominal) obesity. On top of that, the Canadian Center for Functional Medicine as well as the University of Toronto researchers have recently found that higher doses of PGX can diminish appetite to such an extent that even the heaviest individuals have a dramatic and sustainable reduction in appetite. It basically acts in a similar fashion to stomach stapling to reduce food intake.

In addition to curbing appetite by improving insulin sensitivity, preliminary evidence indicates that PGX has powerful effects on reducing regulatory compounds that stimulate appetite like ghrellin while at the same time increasing the levels of regulatory compounds that block the appetite like PYY, CCK, and adiponectin. Further studies being conducted by Dr. Vuksan will likely show that PGX exerts powerful effects on these appetite regulators.

Clinically Proven Effects of PGX

  • Reduces postprandial blood glucose levels
  • Reduces appetite and promotes effective weight loss
  • Increases insulin sensitivity
  • Improves diabetes control
  • Lowers blood cholesterol


With a greater understanding of human physiology and appetite regulation there are emerging approaches to long term weight management that are producing effective answers. While pharmaceutical companies continue to furiously race to discover the perfect pill to control hunger (most of the diet drugs discovered so far are ineffective and dangerous), the real answer may be a unique blend of selected, highly viscous soluble fibers that act synergistically to develop a higher level of viscosity and expansion with water than with the same quantity of any other fiber alone. In addition to its effects on blood sugar levels and improving insulin sensitivity, we believe that one of the key reasons why people lose weight almost effortlessly with PGX is that it greatly reduces appetite.

Key References . . .
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