Below are some myths:
Small changes in food intake and/or exercise will produce large, long term weight changes.
This idea was based on the old idea that 3500 kcal equals 1 pound of weight. But it does not take into account the fact that energy requirements change as body mass changes over time. So, as weight is lost, it takes increasingly more exercise and reduced intake to perpetuate the loss.
Realistic weight-loss goals will keep people motivated.
This idea seems reasonable, but it is not supported by evidence. In fact, several studies have shown that people with very ambitious goals lose more weight (eg, TV's The Biggest Loser).
Slow, gradual weight loss is best for long-term success.
Actually, rapid weight loss via very-low-calorie diets resulted in significantly more weight loss (16% vs 10% of body weight) at 6 months, and differences in weight loss persisted up to 18 months (Int J Behav Med. 2010;17:161-167).
A bout of sexual activity burns 100 to 300 kcal per person.
With intense sexual activity, a 154-pound man burns approximately 3.5 kcal per minute. However, given that the average amount of time spent during one stimulation and orgasm session is about 6 minutes, this man might expend about 21 kcal total. But, he would burn about 7 kcal just lying on the couch, so that amount has to be subtracted, which gives a grand total of 14 kcals of energy expended.
Eating breakfast prevents obesity.
Actually, 2 studies showed no effect of eating vs skipping breakfast.
Adding fruits and vegetables to the diet results in weight loss.
Adding more calories of any type without making any other changes is likely to cause weight gain. Eating fruits and vegetables is healthful, however.
Weight cycling, aka "yoyo dieting," increases mortality.
The data are from observational studies and likely confounded by health status.
Weight Loss Myths PDF (108KB)
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