Low Carbohydrate Diets for Weight Loss

Low carbohydrate diets can come in various forms, the most popular in combination with high protein and fat. The high protein factor is already explained in the chapter on High Protein Diets. This chapter focuses on the low-carb factor.

The Theory

In theory, carbohydrates raise blood sugar levels, which then trigger insulin production. Insulin then drives blood sugar into the cells. This prevents fat breakdown in the body, and prevent weight loss.

Low carbohydrate diets also focus on the role of insulin to regulate hunger and satiety, and fat formation, as promoted by Atkins, and South Beach Diet. The argument is that excessive carbohydrate intake results in high amounts of blood sugar, which in turn over-stimulates insulin production. The large amount of insulin will then cause a drop in blood sugar. The body reacts by craving for more sugar, which starts another cycle of eating.

In very obese people, the body may be insulin resistant. When insulin is released in large amounts, another counter-reacting hormone, adrenalin, is released to raise glucose level to keep blood sugar in a narrow band. With this going on for a long time, the insulin becomes ineffective in transporting the glucose to the cells (insulin resistance). Other than the craving for more sugars, blood sugar is not efficiently transported to the cells (causing diabetes). This excess sugar eventually gets synthesized into stored fat.

It therefore makes apparent sense that decreasing carbohydrate intake will result in lower blood sugar and insulin levels, leading to better weight control. When the body does not have blood sugar to break down, it starts to break down fat.
People do lose weight on low-carbohydrate diets, but many nutritionists argue that the weight loss probably isn't necessarily related to blood sugar and insulin levels. The weight loss could be due to a combination of various factors, mostly due to the result of eating fewer total calories than the body requires for normal daily weight maintenance – a simple matter of the energy equation working.

How weight is lost

The weight loss with low-carbohydrate diets is caused by:
Loss of water. In the initial period, the weight loss is water weight. When one eats little carbohydrate, the body burns its stored carbohydrates (glycogen) first. This releases water resulting in weight loss.

Ketosis / Lipolysis. Atkins claim that the combination of low carbohydrate and high protein and fat forces the body into the state of lipolysis/ketosis and the body starts to burn fat, resulting in weight loss. However, his last book, published in 2003 seemed to have de-emphasized the process of lipolysis/ketosis.

Induced Starvation. A more extreme state of low carbohydrate dieting stimulates starvation, as in very low calorie diets (VLCD). This also loses water weight and later induces the state of ketosis which burns fat. In addition, it also breaks down lean body mass, which leads to a number of side effects. See the chapters on Very Low Calorie Diets (VLCD) and Total Fasts.

Reduced appetite. Burning fat without carbohydrate creates byproducts called ketones that build up in your bloodstream. Under this condition, appetite is suppressed. Once a balanced meal is resumed, the appetite returns. This means that to maintain a reduced appetite in this way, one has to be in a constant state of ketosis – undesirable because of the danger to the kidneys – see the chapter on Very Low Calorie Diets. Other factors that a low carb diet can also produce is that is minimizes insulin rush that can bring blood sugar back so low that it induces another round of hunger. It also avoids the case of insulin resistance created after the body gets worn down trying to balance blood sugar levels – leading to diabetes.

Reduced calories. It’s back to the energy equation. Most low-carbohydrate diets simply end up reducing your overall calorie intake because the diet limits a whole group of foods. This state of energy deficit balance will result in weight loss. So, with this rationale, a low carb diet is just another version of a caloric restriction diet. See the chapter on Diet Success and Calorie Values. Each pound of fat contains 3,500 calories. Lose 3,500 calories and you lose a pound.

Long-term health risks of low-carb diets

The long-term health effects of strictly low-carb diets are largely unknown because most of these, like Atkins and South Beach Diets are modified to include protein and fats. However, results based on these regimens are beginning to get published and, despite misgivings by the official bodies, have shown some arguably favorable results.

One recent one validated that the ketogenic, or low-carb, diet significantly reduces body weight and body mass index. The researchers found that a controlled-carbohydrate nutritional approach decreases the level of tryglycerides, LDL (bad) cholesterol and blood glucose and increases the HDL (good) cholesterol. In addition to long term validation of these health benefits, they also found no significant negative health implications.

A few studies have looked at the benefits and risks but nothing has been conducted over a long enough period to show whether these diets increase or decrease the risk of health conditions that develop over many years, such as heart disease, cancer, and kidney or bone problems. But the American Heart Foundation reaffirmed their official stand not to endorse diets such as Atkins when the media reported that they have changed their original position.

Long term maintenance

Theoretically, in order to maintain weight loss, you need to stay on the program. Evidence shows that a low-carbohydrate diet is just as hard to maintain as other diets. A study of the Atkins Diet, published in the May 2003, found that after one year, four in 10 people dropped out, just as four in 10 people on the traditional calorie-control diet dropped out. The low-carbohydrate diet is no easier than other diets to stay with for a long period of time.

A study followed 18 Atkins dieters for a month. During the 2-week induction period, the dieters consumed 1,419 calories a day, compared with 2,481 calories a day before starting the diet, and lost an average of about 8 pounds. In the next phase, dieters averaged 1,500 calories a day and lost an additional 3 pounds in two weeks. Dieters in both phases cut back on carbohydrates by more than 90%, but the actual amounts of fat and protein they ate changed little. Some patients felt tired, and some were nauseated on the plan. Most indicated that they were eager to go back to their regular diet.

Summary

Notwithstanding all the negative feedback given on low carbohydrate diets, often using Atkins as the benchmark, there is increasing evidence that weights are kept off when carbohydrates (especially the refined ones) are avoided. In the long term low carbohydrate diets may not be any different from other calorie-control diets but it is an alternative.

The proponents of low carbohydrate diets claim the benefits of being in ketosis. Others warn of the dangers. It is probably a question of how the diet is managed – the risks can be reduced by avoiding a prolonged state of ketosis, and supplementing the food with sufficient nutrients. In any case, simply losing 10% of body weight alleviates risk factors associated with overweight. See the chapter on It Should Scare You but You are Not Alone.

There is also increasing feedback that the low carbohydrate fad is fading. The reason is due to the boring menu of these diets. And that could be the reason why low carb diets are no better than other low-calorie diets in keeping people on them for long.

In summary, low-carbohydrate diets appear to work, but no better than low fat/calorie diets. Dieters should be careful not to go into prolonged ketosis; and it takes some measure of discipline to continue with the monotonous menu for the long haul.

Experts who evaluated reports indexed from 1966 to 2003 in MEDLINE found that weight loss was associated with longer diet duration and calorie restriction but not with reduced carbohydrate content. But the last word may still lie with a new low carbohydrate vs low fat diets study sponsored by the National Institutes of Health. They have given a grant of nearly $2.3 million to Kaiser Permanente's Center for Health (which also contributed $100,000) and Oregon Health & Science University to enlist 240 obese patients into this study. We anxiously await the findings.

More on low carbohydrate diets vs. low fat diets are presented in the chapter on Low Fat High Carbohydrate Diets.

References and credits are cited in the printable book.