Chapter summary
- There are over 660 diets, and few have a good long-term record.
- Drop-out figures: 10% quit by Tuesday and 40% by the weekend. Only 20% continue for a month and 10% for a year. After seven years, fewer than 8% keep off a 10% weight loss.
- Early evidence: A 1918 Carnegie Institute trial put 12 men on 1,400 to 2,100 calories a day. The result was hunger. Later work by Leibel and Hirsch showed the body fights weight loss by lowering energy use.
- Most diets are not designed to be kept. People see a diet as short-term deprivation they go “on” and then “off”.
- The best diet is the one you stay with.
Official advice versus the data
- Guidelines (USDA and many countries): Eat fewer calories and move more.
- The evidence: Mann and colleagues (2007) reviewed 31 studies and found one-third to two-thirds of dieters regain more than they lost. They concluded diets are not the answer.
- The counter-argument: Losing weight has real benefits. Each kilogram lost cuts health risk by 3 to 8%, and a 10% loss halves it. Diets may help as a short-term emotional and physical start.
Five lies the weight industry wants you to believe
Dr Rick Kausman, who has run a weight management clinic for 25 years, lists these:
- Willpower: It is a short-term skill and not enough on its own.
- Shaming works: Reality TV does not shame people thin. Compassion and understanding work better.
- Doctors are weight experts: The author says many doctors just repeat the standard line to exercise and eat less. Doctors would say they follow the guidelines.
- Weight loss leaders are experts: Weight Watchers has “life members”, which says that their business depends on failed diets.
- Diets lead to weight loss: Extreme diets can lead to eating disorders and nutrient deficiency.
Do diets differ? The DIRECT trial
- Shai (2008) compared a calorie-restricted low-fat diet, a calorie-restricted Mediterranean diet and an unrestricted low-carbohydrate (Atkins) diet over two years.
- Weight loss: 2.9kg low fat, 4.4kg Mediterranean, 4.7kg low carb. The low-carb group improved cholesterol ratio by 20% compared with 12% for low fat.
- Adherence was 95% in year one and 85% in year two.
- Flaws: The trial mixed restricted and unrestricted diets, and people under-report what they eat.
- Even so, the author concludes low carbohydrate gave more weight loss and metabolic change. Vegetarians may find it hardest. The study authors said personal preference should guide the choice.
Bariatric surgery
- In the US more than 220,000 operations were done in 2009.
- A Belgian 12-year follow-up of lap bands found half were removed and 40% had major complications. Average loss was 42% of excess weight.
- Surgery costs from $14,000 and carries risk, but morbid obesity is also costly and deadly.
Take-away points
- Diets fail in the long term, so plan a lifestyle.
- Successful maintainers often eat breakfast, weigh weekly and exercise.
References
- Shai, I. et al. (2008) Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. N Engl J Med 359(3):229-41.
- Mann, T. et al. (2007) Medicare’s search for effective obesity treatments: diets are not the answer. Am Psychol 62(3):220-33.
- Leibel, R., Rosenbaum, M. and Hirsch, J. (1995) Changes in energy expenditure resulting from altered body weight. N Engl J Med 332:621-628.
- Kennedy, E. et al. (2001) Popular diets: correlation to health, nutrition, and obesity. J Am Diet Assoc 101(4):411-20.
- Himpens, J. et al. (2011) Long-term outcomes of laparoscopic adjustable gastric banding. Arch Surg 146(7):802-807.
- Courcoulas, A. et al. (2013) Weight change and health outcomes at 3 years after bariatric surgery. JAMA.
- Kausman, R. If Not Dieting, Then What?