At the Apex Fitness Group, we receive hundreds of calls every week regarding diet and nutrition. Some of the most frequently asked questions deal with high-protein and fat diets that brand carbohydrates as evil and as the reason for the prevalence of obesity in our society today.

Such diets are not new. They have waxed and waned in popularity over the years, with the previous crescendo occurring in the '70s. The recent popularity most likely stems from the fact that, in spite of previous dietary recommendations and the prevalence of low-fat and non-fat foods, more and more of the population continues to reach obesity. This increase in obesity is because people are not following current diet and exercise recommendations. Let's examine how proponents or marketers of high protein diets trick their patrons. The following are the most prevalent claims made in support of these diets:

Claim 1. People are not getting fat from consuming too many calories, but from the consumption of carbohydrates, especially high glycemic index (GI) ones.
Despite the claims of these diets, obesity and weight gain are the result of positive energy balance. If one consumes more calories than they expend, then there will be an increase in mass. One's genetics and lifestyle determine how easy it is for this to occur. The problem is that society's caloric intake has increased (by about 300 calories in the last decade) and its caloric expenditure has decreased (due to technology and labor-saving devices).

Glycemic index refers to the effect on the blood sugar (BS) level of equivalent amounts of CHO contained in different foods. 6 In other words, how quickly BS rises and how much insulin is released in response to a particular food. GI measures a single food source eaten by itself and on an empty stomach. Several studies have shown that high GI foods do not have the same glycemic response when given as part of a mixed meal. Many, if not most, high GI foods eaten today are refined foods, high in added sugar, and would not be considered wise food choices by any standard.

We must still face the truth, which is that high GI foods, while possibly not the wisest use of calories, are not responsible for weight gain. People get fat when they consume too many calories in relation to expenditure.

Claim 2. Carbohydrates stimulate insulin release, causing the body to store fat. This accompanying insulin production causes insulin resistance (IR) and the development of obesity and NIDDM (type II diabetes). It is interesting that none of these diet proponents mention that protein also stimulates insulin release. Other than genetic IR, most scientists acknowledge that it is obesity itself (due to an excessive energy intake) that leads to IR, not the other way around.

Insulin resistance is often accompanied by several other conditions collectively known as "Syndrome X." Characterized by insulin resistance, hypertension, hyperlipidemia and an increased risk of cardiovascular disease, Syndrome X is usually associated with obesity (especially abdominal), a high-fat diet and a sedentary lifestyle. A result of these factors is high levels of circulating free fatty acids (FFA). In the presence of high FFA concentrations, the body will favor their use as energy, decreasing glucose oxidation, glycogen synthesis, and inhibiting glucose transport. The result of this is hyperglycemia. If blood sugar levels are chronically high, insulin will also be elevated, leading to the conversion of the excess blood sugar to other products such as sugar proteins, and fatty acids. These facts alone seem to bolster the idea that carbohydrates lead to health problems. The truth is that a healthy person would need to eat an extremely high percentage of simple carbohydrates (sweets), a high fat diet, be in an energy excess, or overweight to have chronically elevated blood sugar. The average American eats about 34 percent fat and less than 50 percent carbohydrate in their diet. The consumption of mixed meals with these percentages will not allow blood sugar to be chronically high in a healthy exercising individual. There is some evidence that diets high in sucrose or fructose and fat can lead to insulin resistance and obesity in rats. In either case, the solution is a low-fat diet high in complex carbohydrates. So, how does one become insulin resistant? If one constantly overeats, excess calories are stored as fat. Fat cells then increase in size. The growing fat cell itself becomes insulin resistant and the prevalence of FFA as mentioned earlier will cause the body to favor the use of fat for energy, at the expense of glucose. This becomes a viscous cycle that continues to perpetuate itself. The fatness leads to IR. This leads to impaired glucose use. BS levels rise. Insulin levels rise. Cholesterol, TG and blood pressure rise as well. To make matters worse, the impaired ability of glucose to enter muscle cells keeps glycogen stores lower, which can increase appetite, motivating the individual to eat more, increasing fat stores, exacerbating IR, round and round we go.

As numerous studies point out, high-fat diets are strongly associated with obesity, thus insulin resistance and diabetes. Of course eating fat does not make one fat (same with carbohydrate, as explained later) unless consumed in excess of energy requirements. However, it is easier to consume excess energy (hyperphagia) on a high-fat diet due to fat's small volume of food per calorie. Couple the high intake of dietary fat with excess calories and a sedentary lifestyle and it is easy to envision an abundance of free fatty acids floating around in the blood stream. It is much more likely that a high-fat diet leads to the excess consumption of calories, obesity, insulin resistance and eventually NIDDM than it is that carbohydrates cause insulin resistance and, as a result, obesity. The solution, again, is a diet with the appropriate amount of energy, high in fibrous or starchy carbs, and exercise. In fact, a study of type II diabetics, people with insulin resistance and normal weight people found that three weeks of a high-carbohydrate, low-fat diet and exercise significantly lowered insulin levels.

Claim 3. Low-carbohydrate diets are more effective for weight loss. If one's goal is simply to lose as much weight as possible without regard to composition of weight loss, knocking out carbs may be the way to go. A study comparing short-term weight loss on a ketogenic (very low CHO and high in fat, leading to ketosis) and nonketogenic diet illustrate this point quite clearly. Even though total weight loss was greater on the ketogenic diet, fat loss was essentially equal, water loss was 177 percent greater (due to decreased muscle glycogen and muscle water loss), and protein loss was 88 percent greater on the ketogenic diet. So, for the goal of fat loss, there is no benefit to the ketogenic diet.

The disadvantages, however, would likely be a decrease in 24-hour energy expenditure due to dehydration and loss of lean body mass. Additionally, for most athletes participating in high-intensity exercise, the decreased muscle glycogen stores would impair performance significantly and high-protein diets would decrease testosterone levels when compared with appropriately mixed food intakes, thus having a negative impact on recovery. Finally, there is increasing evidence that a high-fat diet may actually promote body-fat storage in genetically predisposed obese and post obese individuals.

Claim 4. A ketogenic diet offers a "metabolic advantage".
Dr Atkins, in his book Dr. Atkins' New Diet Revolution, states that following his ketogenic diet will allow one to lose weight on a number of calories that once led to weight gain. 26 The state of ketosis that Atkins seeks can be measured by testing for ketones in the urine. This leaves us with the knowledge that in the production and use of ketones for energy, some is excreted (wasted) in the urine. Essentially, calories are just eliminated. For those interested in losing fat while gaining muscle, eating a ketogenic, isocaloric diet sounds very appealing (i.e., eat the calories your body requires but have some wasted in the urine, creating a calorie deficit and, therefore, fat loss). However, this excretion of ketones most likely amounts to only 50 to 60 calories a day, hardly what would be considered a metabolic advantage. The low glycogen stores that are an inevitable result of a ketogenic diet would more likely have negative effects on exercise intensity and appetite, yielding a metabolic disadvantage. 27 Another flaw in the "metabolic advantage" theory is related to the thermic effect of food (TEF). Thermic effect of food measures the increase in metabolic rate in response to the ingestion of food. Studies put this contribution at 5-15 percent of basal metabolic rate (BMR), when consuming a mixed diet. The low end of the range is seen in those eating a high fat diet, and the high end is seen in those eating a high complex-carbohydrate diet. 3 If a person had an absurdly low BMR of 1000 calories, this would translate into a TEF of 50 calories on the high fat diet versus a TEF of 150 calories for a high complex CHO diet. So much for "metabolic advantage".

Missing the Point
What proponents of low-carbohydrate diets seem to miss is the obvious. Even though CHO and protein stimulate insulin release and lead to storage of substrate as FA, it will not lead to long-term fat accumulation unless caloric intake exceeds caloric expenditure for that day, or week, etc. These proponents take a complex series of events (human metabolism), highlight the portion that supports their claim and ignore the big picture. Because humans are periodic eaters, we will always eat more at a sitting than can be immediately used for energy. This influx of glucose, amino acids, glycerol and fatty acids stimulate insulin release so that these materials can be used for energy and stored for later use (as glycogen in liver and muscle and fat stores). 5 As an individual goes through the next several hours without food intake, fatty acids and glucose are liberated from storage depots to fuel metabolic activity that is always occurring.

By the way, in a resting state, fatty acids provide the majority of energy used, regardless of diet composition. We are storing and liberating fat continuously throughout the day. There is absolutely no evidence that a high CHO diet will lead to weight gain if one eats at or below maintenance. In fact, it is impossible. In the end it is caloric intake versus expenditure that determines if one increases or decreases fat stores.

Also, if one looks at the energy cost of converting macronutrients to fat, it requires much less energy to convert dietary fat to body fat than to convert CHO to body fat (5 percent of calories vs. 20-25 percent). 28 A study designed to measure lipoprotein lipase (LPL, a fat storage enzyme) activity in adipose tissue and skeletal muscle on a high carbohydrate or high fat diet inadvertently illustrated this. The study design was to keep participants in calorie balance, so that weight was not gained or lost. Due to the increased TEF, the participants on the high carbohydrate diet had to eat approximately 300 calories more to maintain body weight than the high fat diet group.

Lastly, one of the biggest concerns associated with high-fat and protein diets, is the impact on health of the individual. High-protein diets are known to increase bone-mineral losses (calcium in particular) and tend to include greater intakes of saturated fats and cholesterol, which contribute to dyslipidemia. 29,30 Populations that eat diets lower in protein and fat, and higher in carbohydrates, have the lowest incidences of cardiovascular disease. It is when a culture adopts a Western diet, high in calories, fat and sugar and increases their reliance on technology that obesity and its health problems emerge.

If the preceding information is not convincing enough that high-protein diets are not the answer for long-term fat loss in exercising individuals, consider this: of the 438 initial enrollees of the National Weight Control Registry (having lost an average of 66.0 lbs. for over five years), none were successful by following a low-carbohydrate, high-fat diet. In fact, the common denominator for success dietarily was a low-fat diet with a macronutrient profile of approximately 20 percent protein, 25 percent fat and 55 percent carbohydrate.

This information, from a study published in the Journal of the American Dietetic Association, is the most comprehensive study of its kind to date. Data from many other studies support this.

Before concluding, consider these real-world examples: Endurance athletes, who typically consume between 60-75 percent of their calories from CHO, are some of the leanest people on the planet. Conversely, Inuit Eskimos, who consume only protein and fat, comprise the fattest culture in the world.

A final thought
Much time and energy is spent searching for the causes of obesity. Blame is placed on specific foods, classes of macronutrients and genetics. Adding to the confusion is the erroneous belief that the obese maintain very high bodyweights despite low caloric intakes. Many studies show that as body weight increases, reported caloric intake decreases. A recent study showed that self reported energy intakes in American women are approximately 750-1000 calories below energy expenditures as calculated by the doubly labeled water method. This discrepancy increases as body mass index (BMI) increases. This is more proof that obesity is, at its most basic level, an issue of energy imbalance. This imbalance perpetuates itself through a combination of constantly available, palatable food and a society that promotes a sedentary lifestyle.