UPON ITS DISCOVERY, THE FAT MASS AND OBESITY-ASSOCIATED (FTO) gene was deemed an “obesity gene,” as early human studies showed associations between gene changes in FTO and body mass index (BMI). Does exercise work to reduce weight for those genetically predisposed to gain weight? That is the focus of my writing today. Today we explore the genetics of obesity before turning to exercise and weight.
Have you struggled with being overweight? Is Bill Maher correct when he asserts that we should bring back the so-called fat shaming, chiding obese individuals for their lack of self-control? Are those who are overweight to blame for their weight issues?
What do you think?
- A. Obesity is encoded in our genes to a very large extent.
- B. Obesity is not encoded in our genes to a very large extent.
Obesity and inherited genes
Did you guess A or B? You may be surprised to learn that obesity is, to a very large extent, encoded in our genes. Identical twin studies reveal that the heritability of obesity ranges between 70 to 80 percent. Not many body characteristics have a very high number (height has a higher heritability).
“Aside from the fact that they say it’s unhealthy, my fat ain’t never been no trouble. Mens always have loved me. My kids ain’t never complained. Plus they’s fat.”
― Alice Walker, You Can’t Keep a Good Woman Down Short Stories
Concordance Rate is a term used by geneticists to describe the probability that two people with shared genes will develop the same organic disease. We often regard twin studies as natural experiments to test hypotheses regarding the contributions of genetic factors to variability in characteristics such as height or behavioral characteristics.
Twin studies can help us to estimate the contributions of genetic factors to variability in human traits, but such studies make several assumptions. The most obvious assumption is that the twin pairs had similar environments. While “identical” twins are genetically more similar than dizygotic ones, they are often more environmentally similar. For twin studies, we need to always think about the underlying assumptions.
Epidemiologic studies of common obesity show that monozygotic (“identical”) twin pairs have a concordance rate (0.68) for obesity of double that of dizygotic (“non-identical” or fraternal) twins (0.28).
On the other hand, in adoptee studies, adopted individuals’ weights are more closely correlated with the biological parents’ body mass index (BMI). Inherited genetics have more influence on weight than the shared familial environment.
However, exposure to an obesity-inducing (obesogenic) environment is necessary to develop obesity.
So, what did you guess?
- A. Obesity is encoded in our genes to a very large extent.
- B. Obesity is not encoded in our genes to a very large extent.
If you answered yes, you are correct. The heritability of obesity ranges between 70 to 80 percent. While we have recently witnessed an increase in obesity prevalence, what determines who is lean and who is obese is heavily influenced by weight-regulating genes.
We need to keep obesogenic, highly-processed foods out of reach (to avoid exposing underlying individual genetic factors contributing to obesity risk).
Exercise and obesity
I recently read an article with this unwieldy title:
High-intensity exercise downregulates FTO mRNA expression during the early stages of recovery in young males and females.
Researchers determined the genotype for FTO in 28 untrained individuals, ages 24 to 26. They had the subjects perform an isocaloric (400 kcal) cycle ergometer exercise on two separate occasions.
All subjects performed at two levels (high intensity, at 80 percent of peak oxygen use, and low intensity at 40 percent. Each individual had skeletal muscle biopsies and blood samples taken pre-exercise and following 10 and 90 minutes of passive recovery.
Here are the results:
High-intensity exercise downregulates the expression of fat mass and obesity-associated mRNA and suggests that in addition to nutritional regulation, FTO could also be regulated by exercise.
This 2020 Australian study is the first to suggest that high-intensity exercise creates an environment that favors the downregulation of the fat mass and obesity messenger (FTO) RNA. Messenger RNA is a type of RNA that is necessary for protein production.
High-intensity exercise changes the messages sent by obesity-related genes. Thank you for joining me in this look at the relationship between genes, obesity, exercise, and weight.
The information I provided in this blog is for educational purposes only and does not substitute for professional medical advice. Please consult a medical professional or healthcare provider if you seek medical advice, diagnoses, or treatment. I am not liable for risks or issues associated with using or acting upon the information in this blog.
