Are Low Carb Diets The Best Way To Lose Weight?

Low-carb diets are popular eating plans for slimming down. A low-carb diet is likely to produce weight loss at first, according to the Mayo Clinic. However, a low-carb diet may not be the best way to lose weight over the long term, says registered dietitian Sari Greaves, a spokesperson for the American Dietetic Association. There are pros and cons to low-carb diets.

Definition

The Mayo Clinic defines a low-carb diet as one that limits carbohydrates, such as bread, grains, rice and starchy vegetables, while emphasizing foods with protein and fat. A typical low-carb diet focuses on meat, poultry, fish, eggs and some nonstarchy vegetables, Greaves says. For most people, carbs are the primary source of energy. During digestion, your body converts carbs to sugar. As your blood sugar rises, so does your insulin level. According to the Mayo Clinic, the theory behind the low-carb diet is that rising insulin levels prevent fat breakdown in the body by allowing sugar to be used for energy. The Mayo Clinic notes that proponents of low-carb diets believe a decrease in carbs causes the body to burn stored fat for energy

Types

The Atkins and South Beach diets are the most popular types of low-carb diets, according to Greaves. They follow a rigid format with several diet phases. On the Atkins diet, you start with a two-week "induction" phase in which carbs are severely reduced to 20 g per day. Similarly, the South Beach diet requires a two-week first phase in which virtually all carbs, including fruits, are eliminated. Both diets have a second phase for ongoing weight loss where some carbs are allowed. The Mayo Clinic states that a daily limit of 50 g to 150 g of carbs is typical on a low-carb diet. According to an evaluation of popular diets by the University of Illinois at Urbana-Champaign, the South Beach diet allows more fruits and vegetables than the Atkins diet. The Atkins diet also emphasizes more high-protein foods, such as meats, than the South Beach diet, Greaves adds. Another type of low-carb diet sometimes called the "No White Foods" diet simply eliminates all white, starchy foods from the diet, such as potatoes and white breads, Greaves notes.

Pros

Most people on low-carb diets lose weight at first, according to Greaves, partly because this type of diet reduces hunger. You're likely to feel full longer since a low-carb diet is relative high in fat and protein, which take longer to digest than carbs. Low-carb diets also tend to have a diuretic effect, so you're likely to lose pounds from water weight in the beginning, the Mayo Clinic notes. Calories are restricted on a low-carb diet because it limits the variety of foods allowed, which generally means you'll consume fewer calories overall. Because most people drop weight at first, the low-carb diet can be beneficial at jump-starting a weight-loss program for people who have a lot of weight to lose or dieters who lack motivation. "Seeing the numbers on the scale go down can motivate some people to continue on a weight-loss plan," Greaves points out.

Cons

Low-carb diets are sometimes called heart attack diets because some of them emphasize sources of protein that can be loaded with artery-clogging saturated fat, Greaves says. Following a rigid low-carb diet that is high in red meat and eggs is likely to increase your cholesterol, according to the Mayo Clinic. If you're cutting back on whole grains, fruits and vegetables, you may not be getting adequate fiber, leading to constipation and other gastrointestinal problems. Low-carbs diets may also increase the risk of ketosis, a condition resulting from the incomplete breakdown of fats, according to the Mayo Clinic. Ketosis can cause nausea, weakness, dizziness, dehydration and irritability. Finally, low-carb diets can leave you feeling depressed, according to Greaves. In studies, low-carb diets produced a drop in serotonin levels in lab rats. On the other hand, carbohydrates are believed to increase the levels of this feel-good brain chemical, Greaves says.

Bottom Line

Low-carb diets are probably not the best way to lose weight long-term, according to Greaves, but they may be beneficial for jump-starting weight-loss. FamilyDoctor.org, the web site of the American Academy of Family Physicians, states that low-carb diets have been shown to help overweight people lose weight, and they may work better than low-fat diets when people first start dieting. After the first six months, however, low carb diets don't work any better than other diets, according to FamilyDoctor.org, and can have psychological and physical side effects. The best way to lose weight and keep it off is to follow a healthy, reduced-calorie diet that includes foods from all the food groups, Greaves says.