How a low-carb, high-protein diet affects your body

Originally published in The Ottawa Citizen February 26, 2003
Original Title: A Mars bar a day, pack those pounds away

Increasing numbers of people are adopting low sugar (carbohydrate) high protein diets. Some want to lose weight, others wish to avoid further weight gain as they age. How does this change in dietary habits influence weight control? Does it promote weight loss and is it for everyone?

Variations of these diets (the popular Atkins and Bernstein diet plans) are an outgrowth of diets prepared for diabetic patients. They focus on increasing the use of fat stores to supply the body with energy. The more the body draws on its fat reserves for energy, the greater the likelihood of losing weight. Selecting foods according to their sugar content and consuming foods of good fat and protein quality can help accomplish this goal.

The caveat is these dietary choices must be in balance to provide all the nutrients and compounds necessary to stay healthy.

The body needs a reliable continuous supply of energy to function properly. For example, glucose is the only energy source the brain uses. Any prolonged disruption in supply can lead to confusion, agitation, headache and irritability among other symptoms.

There are systems in place to convert other energy sources (fat and protein) into glucose when glucose levels become too low. Maintaining brain function is a top priority.

Although hormones, the nervous system, and chemical signals from various organs regulate the production and metabolism of blood sugar (glucose) in the body, insulin plays a pivotal role.

As blood glucose levels increase or decrease, insulin respectively rises and falls to maintain normal glucose levels. Insulin also affects fat and protein metabolism that can influence weight loss or gain. Low insulin levels free the body to draw upon fat stores for fuel. High levels lead to fat accumulation and weight gain.

A recent series in the Citizen outlined the effects of obesity and its relation to the high carbohydrate North American diet. Rice, potatoes, bread, pasta and sugar-laced carbonated sodas among others contribute to this problem. The long-term consumption of these foods can lead to weight gain increasing the risk of diabetes.

For example, after eating pizza, a high carbohydrate meal, insulin levels increase rapidly. Sugar levels can remain elevated for several hours because of the type of carbohydrates found in the pizza. Since the body has no need to make any sugar on its own, it uses insulin to block new sugar production in the liver, prevent the breakdown of fat stores and increase sugar accumulation in the body’s tissues.

High carbohydrate meals usually lead to another hungry spell about an hour or two after eating. The rapid decrease in blood sugar due to the elevated insulin levels directly stimulates hunger through a series of hormonal signals to the brain.

Indeed, carbohydrate rich diets can promote a persistent elevated insulin state (hyperinsulinemia) preventing the body from tapping its fat stores for fuel. Over time, insulin will have less effect on the tissues (insulin resistance) just as overusing salbutamol (Ventolin) to treat asthma reduces its desired effect.

When fasting or consuming low carbohydrate foods, the body compensates by keeping insulin levels low producing the opposite effect of insulin resistance. Fat stores and muscle protein provide an alternate energy source. The liver processes the fat and protein to make glucose (gluconeogenesis (new sugar creation)). It can breakdown its own sugar stores (glycogen) releasing more glucose into the blood stream.

The Atkins diet significantly reduces bread, rice, potatoes, cereals and other high sugar-containing foods thereby minimizing insulin secretion after each meal.

For example, a bacon and eggs breakfast does not contain much sugar. Despite the high fat meal, the body will continue to draw energy from its fat stores because there is little insulin to block this effect. However, add home fries or hash browns to this breakfast and you may as well have that pizza.

This does not give everyone carte-blanche to eat whatever low carbohydrate fatty meal they like because there are different qualities of fat. Investigations are ongoing regarding not only what we eat but also what combinations of food promote weight loss as opposed to weight gain.

Blood sugar control has further implications for obese type 2 diabetics. Reducing high sugar levels demands a change of the quantity of food eaten and quality of the carbohydrate consumed. The former is a straightforward, albeit difficult, and the latter requires a new understanding that not all sugar is the same. The body will digest and absorb different carbohydrates at different rates. Someone drinking sugar-laden soda will experience a drastic surge in blood sugar levels compared to someone who eats rye bread.

Next week: How can you compare carbohydrate content in foods? Which ones will reduce the risk of hyperinsulinemia?

Now where did I put that Mars bar?


© Dr. Barry Dworkin 2003

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