Myths About Obesity

Myths About Obesity

By Thomas Biancaniello, MD

Obesity is a hot topic wherever you look – in healthcare, news, electronic media, and schools.  While much is written on the topic in medical and scientific journals, much of what is discussed and practiced is not based on good scientific data, but often on observations and reasoning much of which is either incorrect or not based on the real data that exists. 

In the January 31^st issue of the New England Journal of Medicine, a highly regarded medical journal, an article entitled: “Myths, Presumptions, and Facts about Obesity” by numerous authors explores this discrepancy.  They distinguish between scientifically tested recommendations and that which may be made from observations which often do not take into consideration other factors that affect those observations which are not considered in reaching the conclusions.  What follows is a brief summary of the article.  For those who wish to read the article, the reference is as follows: Casazza K, Fontaine KR, Astrup A et al, Myths, Presumptions, and Facts about Obesity, N Eng J Med 2013; 368(5) pp 446-454. 

Myths

1. Small changes in energy expenditure or intake will produce large, long-term weight changes.  This is based on a model that says the 3500 kcal changes will result in one (1) pound weight changes. This appears hold in the short-term, but in the long-term in one study the predicted with loss of 50 pounds resulted in a true weight loss of only about 10 pounds.
2. Setting realistic goals is important; otherwise patients will become frustrated and lose less weight.  Although this seems reasonable, several studies have shown that more ambitious goals are sometimes associated with better weight-loss outcomes.
3. Large, rapid weight loss is associated with poorer long-term weight-loss outcomes.  Randomized controlled trials (considered to be the best scientific studies) show that in the short-term the very low energy diets are associated with better weight loss.  However, over the long-term there appears to be no significant difference.
4. Diet readiness is important in determining outcomes in patients who request weight-loss treatment.  Unfortunately five (5) trials showed an average weight loss over a median period of nine (9) months of one (1) kg or ~2.2 lbs.
5. Physical education classes play an important role in preventing or reducing obesity in children.  Physical education, as currently provided and even when the number required days is increased has not resulted in consistent changes in Body Mass Index or BMI (weight per height squared to allow comparison amongst patients of different sizes).  There is clearly a level and frequency of activity needed to achieve this goal, but current physical education programs are not sufficient to provide that level.
6. Breast-feeding is protective against obesity.  Although the World Health Organization reports that it breast-fed babies are less likely to become obese in later life, this has not been supported by studies that have better controlled for confounding factors that influence this.  There are of course other good reasons to encourage breast-feeding.
7. A bout of sexual activity burns 100-300 kcal for each participant.  It turns out for period of sexual activity (about 6 minutes) for an averaged sized man in his 30’s, the expenditure is approximately 21 kcal.

Presumptions

1. Regularly eating breakfast is protective against obesity.  Two studies have shown this not to effect weight.
2. Early childhood is the determining period in learning eating and exercise habits that influence weight throughout life.  Although a person’s BMI tends to track over time (tends to be same percentile), this may be more a reflection of genotype (genes) than early learning.
3. Eating more fruits and vegetables will reduce weight gain or produce weight loss, regardless of other behavioral or environmental changes.  Weight is a function of calories-in versus calories-out.  If you consume more in calories than you burn you will gain weight.  So a healthy as consuming fruits and vegetables in the overall picture is, you must limit portion sizes of the good foods as well.
4. Weight cycling (yo-yo diet) is associated with increased mortality.  This may be due to confounding factors that are often associated in individuals with weight problems.
5. Snacking contributes to weight gain and obesity.  Studies have not supported this and there is no consistent association between snacking and BMI
6. The build environment (parks and sidewalks) influences the incidence and prevalence of obesity.  There are only observational studies and no conclusions can be drawn.

There are no easy answers to the problem of obesity.  It is clear that life style modification is essential in controlling and reducing weight.  The overall principle is calories-in/calories-out.  A combination of 40 minutes of regular vigorous exercise  per day (as approved by your doctor) and reduction of portions of both “good” and “bad” foods would be the first steps to improved health.

Thomas Biancaniello, MC, FACC, FAHA

Clinical Professor of Pediatrics, Columbia Doctors

Pediatric Cardiology, Nesconset, NY  11767