Is Obesity Caused By Bad Genes Or Bad Lifestyle?
Author: Dr. Stephen Chaney
In past issues of “Health Tips From the Professor” I have shared some common sense weight loss tips. But what if it is all for naught? What if there is nothing you can do about your weight?
You may have seen the headlines suggesting that obesity in kindergarten is a very strong predictor of obesity later in life. If so, you are probably wondering what that means for your kids or grandkids – and what it means for you. You are probably asking questions like:
- Should you be worrying about that your toddler’s baby fat?
- What can you do as parents and grandparents to protect the ones you love from a lifetime of obesity and all of the health challenges that involves?
- Is there anything you can do about overweight and obesity? Are some people just fated to be obese from childhood on?
What Does the Study Actually Show?
This was a very well done study. It followed 7738 children of all socioeconomic classes who were enrolled in kindergarten (mean age 5.6) in the US in 1998 and followed them through the 8th grade (mean age 14.1) (Cunningham et al, New England Journal of Medicine, 370: 403-411, 2014).
When the children entered kindergarten, 12.4% of them were obese, and another 14.9% of them were overweight. By the time they reached the 8th grade 20.8% were obese and 17% were overweight. Those results didn’t make the headlines. They are similar to many previous studies.
The results that made the headlines were:
- Overweight 5 year olds were 4 times more likely to become obese by age 14 than normal weight 5 year olds.
- 87% of obese 8th graders (14 year olds) had a body mass index above the 50th percentile in kindergarten, and 75% had a body mass index above the 70th percentile.
- Only 13% of overweight 8th graders had been normal weight (<50th percentile) in kindergarten, and only 13% of the normal weight 8th graders had been overweight in kindergarten.
These results are fully consistent with earlier studies showing that overweight toddlers are likely to become overweight teens, and overweight teens are likely to become overweight adults. What was unique about this study (and generated the headlines) was the precision of the statistics.
Does Obesity Begin In Kindergarten?
The answer to that question is clearly yes. However, the more important question is what message we, as responsible health advocates, should be sharing with the general public. Let me break that down to some of the most important questions that you are probably asking.
Is Obesity Caused By Bad Genes Or Bad Lifestyle?
Taken on face value, the results of this study might seem to suggest that genetics is the primary cause of obesity. However, if that is the message we convey to the public, it is likely to simply fuel the perception that most overweight individuals are genetically destined to be obese. There is nothing they can do about it. So, why even bother trying?
However, the authors of the study also noted that the percentage of children aged 6 to 11 who are above the 95% percentile of weight has increased 4-fold between 1963 and 2000. Genetics does not change in a mere 37 years (37 generations maybe). That 4-fold increase in severe childhood obesity is clearly driven by lifestyle changes over the past 30 or 40 years.
While nobody knows the exact percentages, a reasonable interpretation of recent research in this area might be:
- 10-15% of us are genetically destined to be obese. There is little we can do to change our weight, but a healthy lifestyle can significantly reduce our risk of disease.
- 10-15% of us are genetically predestined to be lean no matter what we eat (Yes. Your suspicions are true). Once again, lifestyle has relatively little influence on our weight, but a healthy lifestyle can significantly reduce our risk of disease.
- The other 70-80% of us are genetically predisposed to become obese if we adapt the typical American lifestyle. For most of us lifestyle choices can make a big difference in our weight as well as our health.
So the answer to this question is BOTH. For most of us, obesity is caused by bad genes AND bad lifestyle.
When Should We Intervene?
You probably already know that any extra fat cells we develop in childhood never go away. They are always with us, looking for those extra calories they can store as fat.
This study suggests that by the time we are in kindergarten, the die may already be cast. Those extra fat cells may have already developed.
And, for many people, the time to intervene may be even sooner. This study also showed that birth weight plays an important role as well. Children who weighed 9 pounds or more at birth were 2-fold more likely to be obese in kindergarten than children who weighed less than 9 pounds at birth.
Once again, a small percentage of overweight babies is due to genetics, but it is lifestyle choices during pregnancy that lead to the majority of overweight babies.
The authors of the study noted that most public health initiatives (school lunch programs, lifestyle education programs, etc.) are targeted at school aged children. The authors went on to say that by then it may be too late to have any significant effect on the incidence of obesity in our children.
They suggested that we need to place a stronger emphasis on influencing lifestyle changes that affect the weight of babies at birth and are likely to influence whether or not they become obese by the time they reach kindergarten.
That’s not the realm of public health policy. That’s our responsibility.
What Should We Do?
If You Are Pregnant:
- The old adage “You are eating for two” was never true.
- Aim for an extra 150 calories during the 1st trimester, 300 during the 2nd and 3rd trimesters (That’s 1 or 2 servings of healthy foods).
- Aim for little or no weight gain during the 1st trimester and a total of 20-26 pounds during the last two trimesters (a bit less if you are overweight).
If You Have a Young Child Who Is Overweight:
- Don’t restrict calories. Restricting calories can stunt growth and interfere with normal mental and physical development.
- Encourage your kids to exercise rather than watching TV and playing video games. You may need to set the example, and that’s a good thing for you as well as for them.
- Provide your kids with a healthy diet. For most kids, that means more fruits and vegetables and less sugary beverages, fruit juices, and processed snack foods. That may simply mean that you don’t bring those kinds of foods into your house. Again, that would probably be a good thing for everyone in the family.
I know some of you are saying “My kids won’t eat healthy stuff”. Let me give you my take on that.
When I was a kid, my mom had a pretty simple policy. If I didn’t like what she cooked, I didn’t have to eat it. I could simply wait until the next meal – when she would be serving the same kinds of healthy foods again.
I got the message pretty quick. It wasn’t eat healthy or eat junk food. It was eat healthy or go hungry. I decided early on that healthy was better than hungry.
Now, let me step down from my soapbox and summarize.
The Bottom Line:
1) The latest research suggests that if a child is overweight by kindergarten, they are likely to be overweight for the rest of their lives. So if you want to spare your kids and grandkids from a lifetime of obesity, you want to intervene early.
2) A small percentage of those kids are destined to be obese no matter what they do. However, for the vast majority of them obesity can be prevented by a healthy lifestyle.
3) If you are pregnant, don’t “eat for two”. That is terrible advice. If your pre-pregnancy weight is stable (neither increasing or decreasing), you only need to add a serving or two of healthy foods to your diet during pregnancy. Check with your doctor about the amount of weight gain that is right for you and follow their advice.
4) If you have a young child who appears to be overweight, don’t restrict their calories. Instead, provide them with healthy food choices and encourage them to exercise.
5) Finally, if you have been overweight since childhood, don’t despair. For most of us obesity is a combination of genetic predisposition and lifestyle choices. You can’t your genes, but you can change your lifestyle.
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.