I eat a high-protein diet that is low in carbohydrates because whenever I increase my carbohydrate intake, I feel bigger and/or gain weight. Why is this?
Most likely, a couple of forces are at work here. First, low-carbohydrate diets reduce total body water (dehydrate). This is the water that is held inside muscle cells and is essential for normal and optimal functioning of the cell. It is not extracellular water (water outside of cells), the type that is associated with bloating or holding water. When carbohydrate intake is increased, the amount of water brought into the cells increases, hydrating them. Since water does have weight, your weight can go up, but it is not fat.

The second possibility is that increasing your carbohydrate intake increased your caloric intake above your weight maintenance level, and you started gaining some fat. Reduce some of the protein or fat to compensate for the increased carbohydrate intake, within healthful guidelines, and all will be fine.

Why are people improving their blood lipid profiles on the Atkins Diet?
Because it is a low-calorie diet, people will lose weight. Any weight loss, whether by Atkins diet or other method, will improve blood lipid profiles as well as lower blood pressure, blood sugar and insulin levels. However, if the person cannot maintain the weight loss, then the risk factors return. Maintenance of weight loss with the Atkins diet is unlikely.

Is it true that carbohydrates make a person fat?
If you eat more calories than you expend in energy, then anything can be stored as fat - protein, fat or carbohydrate.

Are high-fat diets best for losing weight?
While you may possibly lose weight on a high-fat diet, keep in mind that every diet has the potential to result in weight loss, no matter how realistic or unrealistic it may be. The formula for weight loss, however, is quite simple: eat fewer calories than you expend during a day.

While many diets try to argue this point and attribute the weight lost on their diet to some special combination of foods or exacting percentage of proteins, carbohydrates and fats, the fact remains that all fad diets are simply low-calorie diets disguised by a marketing gimmick.

Diets that are high in fats are generally also low in carbohydrates. This leads to an increased loss of intracellular water, which dehydrates the body. So in addition to any fat loss due to reduced calories, there can be a significant loss of water weight in the initial stages of these diets. There are approximately 3500 calories stored in a pound of fat. To lose 5-10 lbs in the course of one week (something often claimed or observed) would require a difference between energy consumed and expended of 17,500-35,000 calories! To say that is unlikely would be a gross understatement. So, obviously not all of the weight comes from fat. Much if not most, is the result of water loss. No one has complained that they have been steadily putting on water over the years and can no longer fit into their clothes. The stuff that you grab and hate is not water, but fat. Losing water will not cause the fat to go away.

Ultimately, the method and eating plan used for weight loss must be able to be maintained. If it is not, then it is merely a temporary fix, and when the eating plan is discontinued, weight regain is likely. The National Weight Loss Registry, which tracks those that have achieved significant, long-term weight loss and is run by the Universities of Pittsburgh and Colorado, has documented that not one person has been successful by eliminating or severely restricting one of the macronutrients (protein, carbohydrate and fat).

Therefore, until someone comes up with similar documentation that high-protein or high-fat diets can lead to long-term weight loss, this method cannot be recommended.

Do engineered foods spur a hypertrophic response and initiate fat loss?
No, exercise does. There are some formulated foods provided to patients who are being treated for a major illness or trauma. These foods can provide a rich mix of specific nutrients recommended by a physician. But for those who have a stomach and intestinal tract in good working order, there is no nutritional advantage to using "engineered" foods. They are grossly overpriced and yield no more results than natural food in the adequately fed individual.

I'm trying to lose fat. Should I avoid fruit, wheat products and dairy products?
No. When reducing calories for continuous fat loss (i.e., fitness models or bodybuilders striving for very low body fat levels), these foods (except wheat) may be eliminated as competition nears. Fruit and dairy products lack the substance or bulk of complex foods, so they don't contribute to satiety when calories are extremely low. But calories are calories.

I've heard that insulin resistance causes weight gain, so a high-protein, low-carbohydrate diet is recommended. Is that right?
No. Weight gain from high fat diets usually leads to insulin resistance. Insulin resistance leads to other health problems such as coronary artery disease. The scientific recommendation for almost all insulin-resistant individuals, genetic or acquired, is a low-fat diet, moderate amounts of protein, high in complex carbohydrates and exercise. Insulin resistant individuals gain weight like anyone else - when they eat more calories than they burn. Insulin resistance may depress satiety signals, leading one to overeat.

Explain why switching from a high-protein diet to a high-carbohydrate diet might cause you to feel bloated initially.
Each part of stored glucose (glycogen) contains 2.7 parts water. With a high-protein diet, glycogen stores are consistently low and therefore water content is low, which decreases the cells' efficiency. The bloated feeling will eventually normalize when the body recovers to a properly hydrated state