Myths and Facts About Obesity
I tend to receive my weekly copy of the New England Journal of Medicine with more than a muted enthusiasm. Generally the articles are complex and related to other specialties of medicine that are not relevant to my daily practice. So you can imagine my excitement when I saw an article entitled “Myths, Presumptions, and Facts about Obesity”. I, of course, snatched the up the journal before it mistakenly hit the recycle bin and fired up the blog machine to bring you the very latest info on weight loss. In the article the authors scoured popular and scientific media to identify some myths and presumptions that are widely believed but refuted or not supported by prevailing scientific evidence. I thought that it would be a good idea to share some of the myths with you, the treasured followers of the counter revolution. I am encouraging all of you to take on an iconoclastic bent and refute any ignoramus out there that would propagate these myths in your presence. You can refer them to the January 31, 2013 edition of the New England Journal of Medicine, volume 365, number 5, page 446 to be more precise. Here we go…
Myth Number 1: Small changes in energy balance kept up over long periods of time will produce large, long-term weight changes.
This is based on older data that shows cutting 3500 calories will result in one pound lost. Unfortunately, this number comes from short-term studies of men on extremely low calorie diets (<800/day). It turns out that there is considerable variability among individuals in the way they metabolize that is not accounted for by this research. Further, as body composition changes within a single individual, metabolism will change (see my post Maybe a Calorie Isn’t Just a Calorie for more on this). What that means is that 3500 calories won’t equal a pound under all conditions nor will it be true in all people at all times. It’s not even true for a single individual at different times.
Myth Number 2: Setting Realistic Goals is important because otherwise people will become frustrated and lose less weight.
While this is surely a reasonable assumption, several studies have shown that having greater goals is associated with better weight loss outcomes. There have even been two studies that have shown that taking unrealistic expectations and making them more realistic had no effect on weight loss. I think that if you set the bar high you may be less likely to reach your goal but you will achieve much more than you would have if you set the bar low. This is an axiom that can be applied to all aspects of life, aim high.
Myth Number 3: Large, rapid weight loss is associated with poorer long-term weight-loss outcomes, as compared with slow gradual weight loss.
The opposite has been true in weight loss clinical trials. A meta-analysis showed that even with very low calorie diets and significant early weight loss there was no difference in long-term weight loss compared with less rapid losses.
Myth Number 4: It is important to assess the readiness of the person to change prior to instituting a weight loss regimen.
Readiness does not predict the magnitude of weight loss or treatment adherence in clinical trials.
Myth Number 5: Breast-feeding is protective against obesity.
This is one I’m going to have to change in the next edition of my book (if anyone knows a good author’s agent, please send them my way). In my defense, this was the stance of the World Health Organization who felt there wasn’t publication bias or confounding in these studies. Publication bias comes from the fact that only studies that show one possible outcome are published. The so-called ‘negative’ trials are kept on the shelf. Further inquiry on this topic found significant confounding and bias. These biases were mitigated in a large randomized trial of more than 13,000 children that showed no significant impact of breast-feeding on obesity, positive or negative. There are still many good reasons to breastfeed. It’s just that your child’s future weight is not one of them.
Myth Number 6: A single bout of sexual activity burns 100-300 calories.
I’m sure there are some ironmen and women out there that really get their burn on, but the data shows the number to be closer to 20 calories for the average Joe and Jane.
Now for the presumptions:
Myths were defined by the article as widely-held beliefs that have solid evidence that shows them to be false. Presumptions are widely held beliefs that have no evidence to refute or deny them. They may be true or not, conclusions can’t be drawn with the current state of the evidence.
Presumption Number 1: Regularly eating breakfast is protective against obesity.
Two randomized trials showed no effect, but they weren’t 100% conclusive. One showed that baseline breakfast habits impacted the results.
Presumption Number 2: Eating more fruits and vegetables will lead to weight loss or (some say) weight gain, regardless of other lifestyle or environmental changes.
I am not saying it is bad or good to eat more fruits and vegetables, only that there is no data to support any influence on weight gain or loss).
Presumption Number 3: Yo-yo dieting is associated with increased mortality.
This has been shown in observational studies. Unfortunately, observational studies can only show association but cannot tell you if there is causation. It could be that the factors that lead to yo-yo dieting are what cause the increased mortality, not the yo-yo effect itself.
Presumption Number 4: Snacking contributes to weight gain and obesity.
This has not been supported in clinical trials but it is very difficult for researchers to account for the many variables associated with snacking, such as total calorie intake and the types of foods that are snacked upon. Therefore it is unclear whether this is true or false.
The most important take-away from the information above is that the popular beliefs, especially those espoused by the popular media, are often at best without convincing supporting evidence and at worst completely false (see my post on a case from Dr. Oz, Breakthrough Fat Burning Method). Even if there is strong evidence supporting it, no research study is infallible and conclusions can change over time with further investigation.
Therefore, the only thing to do is to keep up with the literature. If you aren’t able to do that, don’t worry the WLCR is here for you. Just enter your email on the top right of the home page and you’ll receive updates like this one whenever something new or exciting comes out