energy needs of the body
The body needs a continuous supply of glucose to fuel energy metabolism. To maintain tight glucose homeostasis—stability within a corridor of about 70 to 90 mg/dl—the body converts digested nutrients into cellular energy from carbohydrates or synthesizes glucose in the liver from fatty and amino acids by means of gluconeogenesis. These processes complement and back each other up in case any one raw nutrient—carbohydrates, fats, or protein—is temporarily unavailable. While fasting and at relative rest, a 155 lbs (70 kg) individual requires approximately 200 g (7 oz) of glucose during a 24-hour period. The formula to calculate the demand for your particular weight is 2 mg of glucose per kg of body weight for each minute (2 mg/kg/min). These 200 g, are, of course, approximate. The actual number changes depending on the body and outside temperature, levels of additional physical and intellectual activity, and some other factors. “Additional” means above and beyond the body’s regular functionality, such as heart function, breathing, walking, vision, hearing, thoughts, etc. Obviously, the additional activities increase energy needs, and that’s why exercise, physical as well as intellectual, will accelerate commensurate weight loss. Beyond the glucose for energy metabolism, the body needs a continuous supply of fatty and amino acids to build new cells, synthesize hormones, enzymes, vitamins, and other critical substances. Those needs are called plastic, organic, or replacement, meaning to rebuild or to replace dead cells and the substances lost with feces, urine, perspiration, and exhaled air.
If you consume more than the 200 g glucose needed daily, the body will convert the excess into body fat. That’s how you gain fat. The rate of conversion is approximately 1 g of fat for 3 g of glucose. That’s 9 “fat” calories divided by 4 “carbs” calories plus a liberal allotment for the energy required for consumption, digestion, and conversion.
If you consume less than 200 g glucose, the body will “burn” fat to compensate for the shortage at a rate of about 1 gram of fat for every 2 grams of glucose. That’s how you lose fat. Dr. Atkins incorrectly called this process ketosis, because the ketones are the intermediary product of the biochemical reactions which convert fatty acids into cellular energy. The correct name is lipolysis.
Before converting body fat into glucose, the body utilizes fatty acids derived from food. Thus, if you have too much fat in the diet, the body will not “burn” its own fat until disposing of all fat from food. That means consuming above 75 g of dietary fat stops the loss of body fat dead in its tracks.
If you consume less than 75 g of fat, the body will “draw” its own fat to produce enzymes, hormones, vitamins, cell membranes, and other essential substances. That’s how you are losing fat.
If you consume more than 75 g of fat, the body will dispatch the excess right under your skin. That’s how you gain fat.
If you consume less than 53 g of protein, the body will break muscle tissue into the amino acids needed for building cells, neurotransmitters, hormones, digestive enzymes, and other essential structures and substances. The process is called “muscle wasting.” You certainly can lose weight this way, but, for obvious reasons, it isn’t a desirable weight loss, and it isn’t a loss of fat.
If you consume more than 53 g proteins, the body will convert certain excesses into muscle tissue. The stronger the muscles, the more protein they will take. You gain weight that way, but this isn’t from fat, and it is a very desirable weight. However, if you don’t have strong muscles (just like most women and children), the excess will get converted into glucose, and the excess glucose will get converted into body fat. And that’s how you gain body fat from overeating protein.