WEIGHT SENSOR

How much influence do genes have on body weight?

How much influence do genes have on body weight?

»Maes et al. put forward a most comprehensive review of this literature, the results of which provide indisputable support for a heritable component to BMI and fat mass. Heritability estimates fall in the range of 20 to 80 percent when estimated from family studies that compared parent-child and sibling correlations, 20 to 60 percent when estimated from adoption studies, and 50 to 90 percent when estimated from twin studies. For example, in an analysis of over 3.500 twin pairs who were 4 years old, shared environmental factors accounted for 24 percent of variance in weight adjusted for height in boys and 25 percent of the variance in girls.«

From several hereditary studies, it was found that the genetic component of overweight or fat mass seems to be between 20% and 90%. However, it should be noted that through studies such as these the effects of all genes can be measured, but you cannot identify the genes responsible for them. The genes we analyze are certainly only just a part of this 20 % to 90%. Here are a few examples: 

  • Gene ADRB2: in a meta-analysis of 97 studies and 44.833 participants, the poor gene variant was shown to account for a variation in the BMI of 0.24 and approximately 700 g of body weight, respectively. (Kurokawa et al 2008. )
  • Gene FTO: people with the AA genotype showed a 1.04 higher BMI than people with the TT genotype, meaning 1.5kg more. ()

From these two genes (of 8, which we have) a BMI variation of 1.28 can be explained. People with the unfavorable gene profile thus have a higher BMI of 1.28 points on average than people with the favorable profile in these two genes only. This is just a brief overview of 2 genes out of 8. With 10 kg overweight (a 2.9 BMI points variation), these two out of eight gene variations alone cause 1.28 points, ie 43% of the variation. With 20 kg overweight it is 22% of the variation and with 30 kg overweight, 14%. Therefore, genes are not responsible for overweight, but they do have a significant influence on it.

However, you need to be careful: the predisposition for overweight might be interesting but hardly has any real applications. The impact of the genes on how effective certain weight loss strategies (sports or calorie reduction) are in a person is much more important. With a quick search regarding our genes, we found the following numbers:
  • FTO gene and fat sensitivity: people who take in a lot of fat and carry the unfavorable gene variation of this gene have a BMI of about 2.4 points higher than people who take in a lot of fat and have the favorable gene variant. This is a difference of approx. 8 kg!
  • PPARG gene and influence on fat sensitivity: people with the unfavorable gene variant who had a particularly high fat intake through their food, had an average of 1.9 BMI points more than persons with the favorable gene variant who had a particularly high fat intake through the food. This is a 6.6 kg difference!
  • PPARG gene Influence on weight reduction with calorie reduction and exercise: people with the favorable genetic variation lost 4.9% more weight than people with the unfavorable genetic variations.
  • ADRB3 gene Influence on weight reduction through exercise: People with the unfavorable gene variant, who exercise have a 2.98-fold higher risk (298%) of becoming overweight.
  • ADRB3 gene Influence on exercise and calorie reduction: People with the unfavorable gene variant lost 0.73 kg less weight than people with the favorable gene variant.
  • APOA5 gene Influence on weight reduction efficiency: People with the favorable gene variant reduced their BMI by 13.4%, while people with the unfavorable gene variant reduced their BMI by 0.4% with the same effort.
  • APOA2 gene and fat sensitivity: People who take in a lot of fat and have the unfavorable gene variant have on average a 6.2% higher BMI than people who take in a lot of fat and carry the favorable gene variant. This is again a variation of about 6.3 kg!