Obesity: Nature or Nurture?

Some people collect dolls, others collect coins. I collect articles on obesity. I am most interested in the psychological and social contributors because I feel that is where intervention can make a difference. As a gastroenterologist, I treat several illnesses, such as fatty liver and acid reflux, which are affected by patients’ weight. As a result, I spend a good part of my day trying to motivate people to lose weight, to improve their health. Somewhere between 20 and 35% of adults are obese worldwide and about 6% are severely obese. Here are some excerpts from my collection of articles that contribute to our understanding of this disease.

Psychological:
-Young girls who were told that they were too fat at age 10 were statistically more likely to be obese at age 19, even after accounting for their actual initial weight. This was worse if a family member had told them that they were obese (JAMA Pediatr 2014 quoted online in Endocrine Today May 1 2014).
– Obese people who were told that obesity was a disease were less likely to be critical of their bodies (which is a good thing) but also less likely to make healthy choices, presumably because they felt they had no control over their weight (not a good thing).
– If your friends are of normal weight, you are more likely to be of normal weight.
– A study on self compassion revealed that women who were asked to eat sweets as part of what they thought was a taste test experiment and were told that everyone eats this stuff and not to feel bad about it ate LESS after that message than those who were presented the food without the message (these were women who were dieters or who had guilt feelings about foods). (from Go Easy on Yourself, a New Wave of Research Urges, The NYT March 1, 2011 about the book “Self-Compassion: Stop Beating Yourself Up and Leave Insecurity Behind” by Dr. Kristin Neff)

Genetics:
– Adoption studies show that adopted people are much more likely to have a body mass index similar to that of their birth parents than to that of the family who raised them.
– Identical twins have almost the same weight as their twin, and same body shape, whether they are raised together or separately.

Biology/genetics:
– Basal metabolic rate (resting metabolism) is responsible for about 70% of a person’s energy expenditure. This is influenced by genetics and by muscle mass (muscle burns more calories at rest than does fat).
– More recently, experiments have shown (in lab animals), that differences in animals’ gut bacteria can lead to obesity in some animals. How this applies to humans is unclear.
– Certain medications, such as anti-depressants and mood stabilizers, can cause weight gain.

Lifestyle/Environment:
– People who watch more than 2 hours of TV daily, weigh more. Sitting in front of the TV is worse than being sedentary at work, possibly because people eat and watch TV at the same time.
– Sleep deprivation leads to an increase in the appetite stimulating hormone ghrelin and decrease in the satiety hormone leptin and leads to increased hunger and craving for “comfort food”.
– The obesity epidemic seems to have taken off when we began to eat more processed foods and substituted carbohydrates for fats. One theory is that eating simple carbohydrates raises blood sugar levels quickly, which then raises insulin, leading to increased hunger.
– Foods associated with weight gain over time: potatoes, potato chips, red meat, processed meats, sugar sweetened beverages including fruit juices.
– Foods associated with a lower likelihood of weight gain: whole grains, fruits, nuts, yogurt.

What does one do with all of this information?

First, as a friend, family member or health care provider is to not see obesity as a failure of will, motivation or character and to avoid stigmatizing other people (or ourselves).

The second is gentle encouragement for people to take care of themselves (which may include better eating, sleep and exercise habits), including the recognition that we all have good days and bad days.

It can be hard for people to change their lifestyles but most patients can improve their health if they are motivated and stick to it. It is important to concentrate on making these changes for good health, rather than solely the number on the scale.

It is especially important to give this message to teens, as concentrating on weight/appearance can backfire. People who are overweight and exercise can be healthier than people of normal weight who do not exercise. Exercise has been shown to improve fatty liver, even in the absence of weight loss. And, relatively small changes, ie weight loss of 10%, can make a significant medical difference in terms of health (fatty liver, diabetes, cholesterol and acid reflux) as pointed out by Dr. Nathan in her blog.

Editor’s Note: Here is the link to Dr. Korenman’s excellent article with many practical tips about motivation and eating mindfulness that have been beneficial to her in taking care of herself.

Some interesting recent articles:

Jou, Chin . The Biology and Genetics of Obesity-A Century of Inquiries. New England Journal of Medicine 2014 370:20, 1874-7.
Ludwig, David S. and Friedman, Mark I.” Always Hungry? Here’s Why” The NYT May 18, 2014