The “fat gene” accounts for less than 1 percent of the differences in size between people.
To date, there have been about a hundred genetic markers connected in obesity, but when you put them all together, in total, they account for less than 3 percent of the difference in body mass index (BMI) between people. You may have heard of the “fat gene”, called FTO, short for fat mass and related to obesity). It is the gene most strongly linked to obesity, but it explains less than 1 percent of the difference in BMI between people, just 0.34 percent.
As I discuss in my video The role of genes in the obesity epidemicFTO codes for a brain protein that appears to affect our appetite. You are one of the billions of people who carry over the FTO susceptibility genes? It doesn’t matter because it only shows result to a difference in intake of a few hundred extra calories a year. The energy imbalance that has led the obesity epidemic is on the order of hundreds of calories a day, and that’s the gene known so far to have the greatest effect. The odds of accurately predicting obesity risk based on FTO status are “only slightly better than flipping a coin.” In other words, no, these genes don’t make you look fat.
When it comes to obesity, the power of our genes is nothing compared to the power of our fork. Even the small influence that the FTO gene has shows up to be weaker among those who are physically active and may be was abolished entirely to those who eat healthier diets. FTO appears to only affect those who eat diets higher in saturated fat, which is found mainly in meat, dairy and junk food. Those who eat healthier appear to be at no greater risk of gaining weight, even if they inherited the “fat gene” from both parents.
Normally, the status of the FTO gene does not seem to affect our ability to lose weight. Psychologically, aware we are at increased genetic risk for obesity may motivate some people to eat and live healthier, but it may cause others to throw their hands in the air in fatalism and resign themselves to the thought of this happening in their family, as you can see in the chart below and at 2:11 in my video. Obesity tends to run in families, but so do poor diets.
Comparing the weight of biological and adopted children can help tease the contribution of lifestyle over genetics. Children increasing with two overweight biological parents were found to be 27% more likely to be overweight themselves, while adopted children placed in a home with two overweight parents were 21% more likely to be overweight. So genetics does play a role, but that suggests it’s more the children’s environment than their DNA.
One of the most impressive examples of the power of diet on DNA comes by the Pima Indians of Arizona. As you can see in the chart below and at 3:05 in my video, not only that I have among the highest rates of obesity, but also I have the highest rates of diabetes in the world. That’s it which is assigned to their relatively fuel-efficient genetic makeup. Their tendency to store calories may have served them well in times of scarcity when they lived on corn, beans, and squash, but when the area “settled,” their water source, the Gila River, was diverted upriver. Those who survived the ensuing famine had to abandon their traditional diet live off government nutrition programs and chronic disease rates skyrocketed. Same genes, but different diet, different result.
Actually, it was a natural experiment series above. The Pima who live on the border in Mexico come from the same genetic pool, but have been able to maintain more of their traditional lifestyle, sticking to their basic staples of beans, wheat flour tortillas, and potatoes. Same genes, but seven times less obesity and about four times less diabetes. You can see these graphs below and at 3:58 and 4:02 in mine video. Genes may load the gun, but diet pulls the trigger.
Of course, it’s not our genes! Our genes didn’t suddenly change 40 years ago. But at the same time, in a certain sense, it could be considered that it is all in our genes. This is the subject of my next video The Thrifty Gene Theory: Survival of the Fattest.
This is the second in a series of 11 videos on the obesity epidemic. If you missed the first one, check it out The role of diet versus exercise in the obesity epidemic.
