Some of the most popular assumptions about weight loss are just not true, a new study finds.
Researchers sought the supporting scientific evidence for a variety of widely believed truths about obesity. They found that false and scientifically unsupported beliefs about the topic are pervasive in both the scientific literature and the popular press.
Try to identify the myths in this list:
Small changes in your diet or exercise can cause steady and sustained weight loss.
Setting realistic goals is important.
Slow, gradual weight loss is better than large, rapid weight loss.
If you wait until you feel ready to lose weight, you'll succeed.
Physical education classes now help prevent or reduce childhood obesity.
Breast-feeding helps prevent obesity.
An act of sexual activity burns 450 kilojoules.
The study, published in the New England Journal of Medicine, found that none of these statements had enough evidence to support them as fact.
"This is a wake-up call. We need to remember to ask where the data are even when an idea makes sense," said study author David Allison, director of the nutrition obesity research centre at the University of Alabama, Birmingham.
Because people feel some familiarity with the topic, they may be less prone to question assumptions related to obesity, said Allison. "After all, everybody eats."
Sloppy science making things worse
Allison is concerned that sloppy science associated with the topic of obesity leads individuals astray as they struggle to lose weight. He also believes it negatively affects public health because programmes that won't work receive funding.
"It's an ethical obligation to be honest. It's great to be enthusiastic, as long as you're promoting something you know is true," he said.
The research team behind the new study represented a wide range of specialties associated with obesity, including nutrition sciences, exercise, public health, paediatrics, health policy and biostatistics. The researchers first listed the beliefs related to obesity that they felt were widely discussed and related to issues of public health, said Allison. Then they confirmed that the beliefs were prevalent in research or the media. Next, they collected all the evidence they could find for each belief and used the information to categorise the beliefs as either true, not true or without clear evidence one way or the other.
To find that a belief had clear evidence, one way or another, there had to be randomised controlled experiments - the gold standard of research - supporting or refuting it. Unclear evidence meant there were ambiguous studies, old randomised experiments or just observational evidence.
The researchers also looked at presumptions related to obesity, such as the value of eating breakfast, early childhood habits, the value of fruits and vegetables, yo-yo dieting, snacking, and sidewalk and park availability.
All these topics lacked randomised, controlled studies to support commonly held beliefs, according to the study.
"My surprise [in doing this research] was if you really hold to a scientific level - what do we know with certainty - it was low," Allison said. What's needed, he said, are more randomised trials related to obesity.
Amy Jamieson-Petonic, a registered dietitian and program manager at Cleveland Clinic Wellness Institute, in Ohio, said she's concerned that research emphasising the myths associated with obesity will discourage people who need to lose weight.
"I want people to know it's worth trying, it's worth taking steps," she said. "Our lives are so busy and so full, it takes effort to make a commitment to this."
So, what really works when it comes to losing weight? Allison said strategies shown to be effective include: weight-loss surgery for very obese people; structured weight-loss programmes; regular meetings with a physician, dietitian or coach; defining for people exactly what they should and should not eat; and receiving prepared meals or shopping lists.
The bottom line for weight loss, said Allison, is indeed a fact: "Eating less energy than one expends for a prolonged period of time, and then maintaining that over a period of time."
Learn more about obesity from the U.S. National Library of Medicine.
(Copyright © 2012 HealthDay. All rights reserved.)