HealthDay News — Many commonly held beliefs about obesity and weight loss are not supported by scientific evidence, results of a literature review suggest.

Seven myths and six presumptions about obesity were prevalent on social media and in scientific literature, mostly related to false or unsupported claims about caloric intake or expenditure and dieting, as well as breast feeding, environment and types of food eaten, Krista Casazza, PhD, RD, from the University of Alabama at Birmingham, and colleagues reported in New England Journal of Medicine.

They also identified nine evidence-supported facts, including the role of genetics in obesity and that realistic changes to lifestyle and environment can lead to weight loss.

Continue Reading

“When the public, mass media, government agencies and even academic scientists espouse unsupported beliefs, the result may be ineffective policy, unhelpful or unsafe clinical and public health recommendations, and an unproductive allocation of resources,” the researchers wrote.

Casazza and colleagues performed internet searches of mass media and published studies to determine common misperceptions related to weight gain or loss and obesity. They defined myths as claims that persist despite contradicting evidence, and presumptions and misconceptions as beliefs not supported by scientific evidence.

Weight-loss myths included the following beliefs:

  • Small changes in calorie intake or expenditure accumulate to produce large weight changes over the long term
  • Large, rapid weight loss is associated with poorer long-term weight-loss outcomes than gradual weight loss
  • Diet preparedness is an important element of weight-loss success
  • Breast feeding protects against obesity
  • Sexual activity can burn up to 300 Kcal per person

Presumptions related to obesity included the idea that he idea that eating breakfast is protective against obesity; eating more fruits and vegetables encourages weight loss or decreases weight gain without other behavioral or environmental changes; and snacking is a contributor to weight gain and obesity.

The researchers also identified several misconceptions about activity and environment. These included the perception that exercising and eating habits learned in early childhood shape lifelong habits; the association of wide, rapid fluctuations in weight gain and loss with worse mortality; and that the presence or absence of parks and other environmental places that encourage fitness can help or hinder obesity.

“Many of the myths and presumptions about obesity reflect a failure to consider the diverse aspects of energy balance, especially physiological compensation for changes in intake or expenditure,” the researchers wrote.

They contend that public health efforts to counteract weight-loss and obesity misconceptions and myths should focus on the following nine evidence-based facts: 

  • Recognizing genes as a large contributor to obesity, but not one that cannot be overcome with sufficient environmental influence
  • The importance of lower caloric intake in weight management strategies
  • The positive effect of exercise on health
  • The necessity of sufficient exercise as a routine activity to maintain weight loss
  • The importance of involving parents and families in weight-loss and management strategies for overweight children
  • Incorporating structured meals and meal replacements as weight-loss aids
  • The utility of pharmacological agents in effective weight-loss strategies
  • Recognizing bariatric surgery as a viable option for long-term weight loss, and to decrease rates of incident diabetes and mortality

“The myths and presumptions about obesity that we have discussed are just a sampling of the numerous unsupported beliefs held by many people,” the researchers acknowledged.


  1. Casazza K et al. N Engl J Med 2013; 368: 446-454; doi:10.1056/NEJMsa1208051.