At any given time there are large numbers of people who are attempting to lose weight. For example a survey conducted in Denmark found that 25% of people classified as underweight were slimming (1). The results for all BMI categories are in Table 1
PROPORTION SLIMMING IN THE DIFFERENT BMI CATEGORIES BASED ON SURVEY CONDUCTED IN DENMARK
|BMI category||% attempting to lose weight|
A survey of 16,486 university students in 21 European countries found that only 8% were overweight and that less than 1% was obese. Nevertheless many of them perceived themselves to be overweight. Consequently 44% of women and 175 of men were trying to lose weight. It was also observed that 14% of women and 35% of men were dieting (2).
In the USA, 118,265 men and women located all over the country participated in a telephone survey T he results showed that 29% of men and 44% of women were trying to lose weight. This included 28.7% of women and 8.6% of men with a BMI that was normal. For those who were overweight as determined by BMI the values were 59.6% for women and 35.7% for men. In fact only 1/3 of the men trying to lose weight were classed as obese. For women only ¼ were obese (3).
According to information provided by Data Monitor the diet industry in the UK is worth about £1BN but only about 1% of slimmers manage to maintain weight loss for more than a year. In Australia 6 million people engage the services of a weight loss industry adviser every year. Of these, 80% fail to follow through the programme. Of those who successfully lost weight initially, 95% re-gained it within 1 year (Curtin University Medical Research).
An assessment of Weight Watchers in the USA found that only 6% of clients reach their goal weight at the outset but that less than 1% maintained the goal weight for 5 years(4).
The usual approach is to exercise control of calorie intake.
Only 7 out of 121 morbidly obese patients who had lost weight by fasting followed by semi-starvation remained below their starting weights when followed up about 7 years later(5).
In a review of scientific reports on the treatment of outpatients for obesity only 25% of patients lost more than 8kg and only 5% lost more than 16kg.The authors concluded that the results are:
“remarkably similar and remarkably poor”(6)
In a recent study over 800 patients considered to be overweight by about 20kg, on average, were advised to follow a specific diet for 2 years. Each diet was designed to reduce calorie intake by the same amount (750 calories per day) but the proportions of fat, protein and carbohydrate varied. About 80% of the participants completed the trial. Most of the weight loss occurred in the first 6 months but after 12 months, the body weight was slowly regained so that the average weight loss was only 4kg(7).
In the early 1990s a technology assessment conference in the USA evaluated the widespread attempts to lose weight. The following conclusions were reached:
- At any given time , up to 40% of women and 24% of men are trying to lose weight
- Those who successfully remain on the weight loss programmes usually lose about 10% of their weight
- Up to 2/3 of the weight lost is regained within 1 year
- Almost all weight lost is regained within 5 years
- Weight loss is associated with increased mortality
- Many who are not overweight, especially young women are attempting to lose weight, which may have adverse physical and physiological consequences(8).
There are many other reports which all agree that while calorie restriction may result in weight loss in the short term, the proportion of slimmers who are successful in achieving permanent reduction in weight is extremely small. It is rather significant that this is actually recognised by many of those who regard overweight and obesity as a serious health issue. According to the Foresight report:
“There are few interventions that successfully reduce the prevalence of obesity and none on a population scale”
The “Handbook of Obesity” is a textbook edited by 3 of the leading lights in the field of obesity states that:
“Dietary therapy remains the cornerstone of treatment and the reduction of energy continues to be the basis of successful weight reduction programs.”
However it goes on to say that the
results of such energy-reduced restricted diets are:
“ known to be poor and not long-lasting.”
- H Bendixen et al (2002) Obesity Research 10 (9) pp 911-922
- F Bellisle et al (1995) International Journal of Obesity and Related Metabolic Disorders 19 (10) pp723-730
- Mary K Serdula et al (1999) Journal of the American medical Association 282 (14) pp 1353-1359
- E J Drenick & D Johnson (1978) International Journal of Obesity 2 (2) pp 123-132
- A Stunkard and M McLaren-Hume (1959) Archives of Internal Medicine 103 pp79-85
- F M Sacks et al (2009) New England Journal of Medicine 360 pp.859-873
- Consensus Development Conference(1992) Annals of Internal Medicine 116 pp942-949.