Crash dieting implies losing a lot of weight very quickly. For many years, the term crash diet has had negative connotations, and conventional wisdom suggests that the more quickly you lose weight, the more likely you are to regain it. MayoClinic.com suggests that a healthy rate of loss is 1 to 2 lbs. a week. Losing weight quickly requires extreme effort, which can be difficult to sustain over time, and may lead to loss of lean tissue instead of fat.
Background
Many low-carb dieters report a quick initial weight loss. Dr. Robert Atkins suggested you can lose up to 15 lbs. in the first two weeks of the Atkins diet, followed by a more sustained level of loss after the first few weeks. Low-carbohydrate diets have been in use since the 1970s when Dr. Atkins wrote "Dr. Atkins Diet Revolution." Before Atkins, most weight loss plans involved restriction of fat and calories, combined with increased exercise to bring about weight loss. Since the publishing of "Dr. Atkins Diet Revolution" in 1972 and the subsequent 1992 publishing of "Dr. Atkins New Diet Revolution," low-carbohydrate diets have grown in popularity.
Identification
Atkins, Zone, Protein Power and South Beach are all low-carbohydrate diets. Each of the diets restricts carbohydrate intake in some manner. For example, Atkins suggests eating fewer than 20g of carbohydrates per day from leafy green vegetables in early stages of the diet. The Zone Diet suggests eating 30 percent of your calories at each meal from favorable carbohydrates, such as fruits, vegetables and whole grains. Protein Power suggests limiting carbohydrates to 7 to 10g per meal or snack and less than 30g per day, but doesn't restrict the type of carbohydrates you can eat. South Beach recommends eating mostly vegetables and low glycemic index fruits and grains. Each of these diets has some level of carbohydrate restriction. Fruit, starchy vegetables, potatoes, corn, rice, sugar and grains are all carbohydrate foods restricted on low-carbohydrate diets.
Theories/Speculation
Bethesda Naval Medical Center suggests that the initial quick weight loss experienced on low-carbohydrate diets comes from water loss. When carbohydrates are stored in the body, they are stored at a ratio of 3 parts of water to 1 part of carbohydrates. When you deplete your body's stored carbohydrates, you lose a lot of water very quickly.
In "Good Calories, Bad Calories," Gary Taubes explains that insulin is the key to fat loss on low-carb diets. Limiting carbohydrates keeps your blood glucose levels steady. When your blood glucose levels remain consistently low, your pancreas doesn't release insulin. Because insulin is a fat-storage hormone, it keeps the fat trapped in your fat cells when it is present in the bloodstream. In its absence, your body uses stored body fat as its primary source of fuel.
Research
Research suggests that low-carb diets do bring about a faster initial rate of weight loss than low-calorie, low-fat diets do. A study done at University of Philadelphia and printed in "The New England Journal of Medicine" showed just that. After following both low-carbohydrate and low-fat dieters for a year, researchers noted approximately 4 percent greater weight loss in the low-carb group during the first three to six months of the trial; however, after a year both groups had similar rates of weight loss.
Tufts University nutrition professor Dr. Susan Roberts studied 36 years of research data on crash diets. She suggests that crash diets can work, provided you go about them correctly. Her conclusion was that crash dieting can bring about long-term success if it is achieved through a healthy, calorie-cutting diet. In other research, Dr. Roberts also suggests that the type of calories you eat may make a difference, and that low-glycemic carbohydrates may play a key role in weight loss for many.
Considerations
MayoClinic.com suggests that low-carbohydrate diets are frequently high in saturated fat and cholesterol, which can lead to increased risk of heart disease and cancer. The diets are also often low-fiber diets, which can cause intestinal problems such as diverticulitis or constipation.
References
- MayoClinic.com: Fast Weight Loss: What's Wrong with It?; Donald Hensrud, M.D.
- "Dr. Atkins New Diet Revolution"; Robert C. Atkins, M.D.; 1992
- "Enter the Zone"; Barry Sears, Ph.D. and Bill Lawren; 1995
- "Protein Power Lifeplan"; Michael R. Eades, M.D. and Mary Dan Eades, M.D.; 2000
- "The South Beach Diet Supercharged"; Arthur Agaston, M.D. and Joseph Signorile, Ph.D.; 2009
- Bethesda Naval Medical Center: What About Low-Carb Diets
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