What are we really "designed" to eat? What do paleolithic fossil records and ethnographic studies of 180 hunter/gatherer groups around the world suggest as the ideal human diet?

For several million years, humans existed on a diet of animals and vegetation. It was only with the advent of agriculture a mere 10,000 years ago - a fraction of a second in evolutionary time - that humans began ingesting large amounts of sugar and starch in the form of grains into their diets.

Indeed, 99.9% of our genes were formed before the advent of agriculture. In biological terms, our bodies are still those of hunter-gatherers.

While the human shift to agriculture produced indisputable gains for man; societies where the transition from a primarily meat/vegetation diet to one high in cereals show a reduced lifespan and stature, increases in infant mortality and infectious disease, and higher nutritional deficiencies.

Furthermore, nutritionists at the Harvard School of Public Health have recently publicly criticized USDA’s Food Pyramid recommendations of a diet based on 6-11 servings daily of breads, cereals, rice and pasta. Contemporary humans have not suddenly evolved to incorporate the high carbohydrates from starch and sugar-rich foods into their diet. In short, we are consuming far too much bread, cereal, pasta, corn (a grain, not a vegetable), rice, potatoes, donuts, bagels, cakes, and sodas with very grave consequences to our health. These foods suppress the immune system, contribute to allergies, and are responsible for a host of digestive disorders. Making matters worse, most of these carbohydrates come in the form of processed food.

It is no coincidence that 65% of Americans are overweight, and 27% clinically obese, in a nation addicted to sesame seed buns on their hamburger, with a side of fries and a soda. It is not the fat in the foods we eat but, far more, the excess carbohydrates from our starch and sugar-loaded diet that is making people fat and unhealthy, while leading to epidemic levels of a host of diseases such as diabetes. Even though there is a low-carbohydrate craze taking over every food label and restaurant menu, many people don't really know what a carbohydrate is. Most people will say carbohydrates are sweets and pasta. They may also reply that vegetables and fruits are food types that can be eaten in unlimited amounts without gaining weight.

This may come as a surprise, but all of the above sweets, pasta, vegetables, and fruits are carbohydrates. Carbohydrates are merely different forms of simple sugars linked together in polymers…something like edible plastic.

It is, however, actually a bit more complicated than that. Any carbohydrates not immediately used by the body will be stored in the form of glycogen –— a long string of glucose molecules linked together.

Carbohydrates and Insulin: Friend or Foe?

The body has two storage sites for glycogen: the liver and the muscles. The glycogen stored in the muscles is inaccessible to the brain. Only the glycogen stored in the liver can be broken down and sent back to the bloodstream so as to maintain adequate blood sugar levels for proper brain function, an organ which uses glucose as its primary energy source. In fact, the brain gobbles more than two thirds of the circulating carbohydrates in the bloodstream while the body is at rest.

The liver's capacity to store carbohydrates in the form of glycogen is very limited and can be easily depleted within ten to twelve hours. So the liver's glycogen reserves must be maintained on a continual basis. That is why we eat carbohydrates.

If you are an average person, you can store about three hundred to four hundred grams of carbohydrate in your muscles. However, it is in the liver that carbohydrates are accessible for glucose conversion, and can store only about sixty to ninety grams. This is equivalent to about two cups of cooked pasta or three typical candy bars, and it represents your total reserve capacity to keep the brain working properly.

Once the glycogen levels are filled in both the liver and the muscles, excess carbohydrates have just one fate: to be converted into fat and stored in the adipose, that is, fatty tissue.

Any meal or snack high in carbohydrates generates a rapid rise in blood glucose. To adjust for this rise, the pancreas secretes the hormone insulin into the bloodstream, which lowers the glucose. Insulin is essentially a storage hormone, evolved to put aside excess carbohydrate calories in the form of fat in case of future famine.

High insulin levels also suppress two other important hormones - glucagons and growth hormones - that are responsible for burning fat and sugar and promoting muscle development respectively. So insulin from excess carbohydrates promotes fat, and then wards off the body's ability to lose that fat.

In other words, when we eat too much carbohydrate, we are essentially sending a hormonal message, via insulin, to the adipose cells. The message: "Store fat." Cravings, usually for sweets, are frequently part of this cycle, leading you to resort to snacking, often on more carbohydrates. Not eating makes you feel shaky, moody and ready to "crash." If the problem is chronic, you never get rid of that extra stored fat, and your energy is adversely affected.

Does this sound like you? This can be termed insulin resistance, or IR. Like many problems, IR is an individual one, affecting different people different ways. You must determine if you are carbohydrate intolerant, and if so, to what degree.

Any time your cells are exposed to insulin, they will become more insulin resistant. That is inevitable, but we can control the degree of resistance. An inevitable sign of aging is an increase in IR. That rate is the variable. If you can slow down that rate, you can become a centenarian - a healthy one.

The Solution: The right carbs, the right amount

The best suggestion for anyone wanting to utilize more fats is to moderate the insulin response by limiting (ideally, eliminating) the intake of refined foods which evoke a stronger and/or more rapid insulin reaction, and keeping all other carbohydrate intake to about 40% of the diet. Generally, non-carbohydrate foods (proteins and fats) don't produce much insulin.

Consumption of natural fiber with carbohydrates can reduce the extreme blood sugar reactions described above. Low-fat diets cause quicker digestion and absorption of carbohydrates in the form of sugar. By adding some fats to the diet, digestion and absorption is slower, and the insulin reaction is moderated.

Dr. Atkins provided a major jumpstart to help establish the connection between obesity and insulin, and it is encouraging to see some major studies validate this approach. However, his program labeled all carbohydrates as bad. Some people indeed require up to two-thirds of their diet as vegetable carbohydrate. Diets really need to be modified and adjusted to fit each specific person with his or her own unique genetic requirements. This is why studies that evaluate Dr. Atkins’ approach are not able to consistently validate its effectiveness.

Diets based on choice restriction and calorie limits usually fail. People on restrictive diets get tired of feeling hungry and deprived. They go off their diets, put the weight back on (primarily as increased body fat), and then feel bad about themselves for not having enough will power, discipline, or motivation. Weight loss has little to do with willpower. Getting information from reliable sources and knowledge of the body’s physiology however, has allowed people to successfully transform their physique as well as their lifestyle.

If losing weight made it to the resolution list again for 2005, don’t fret. If you change what you eat, you won't have to be overly concerned about how much you eat. By following a diet based on nutrient-dense carbohydrates, good fats and adequate protein, you can eat enough to feel satisfied and lose fat without obsessively counting calories or fat grams.

Frances Haddock, M. S., is a wellness consultant and trainer in Miami, where she helps individuals reach optimal health by transforming mind and body.