A Simple Guide To Body Genetics (And How They Affect Your Health)
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How many of you have been here before? You start a new fitness program and you’re completely committed, determined to make this the one that sticks. You buy new sneakers, cute workout clothes, and make your grocery lists religiously.
You get to the gym, sweat a lot, hurt a lot, eat clean, say no to tasty things, and go to sleep feeling accomplished.
But then a few weeks go by and the anxiety starts to creep in. You’re not seeing the changes you want to be seeing and you start to doubt yourself.
Is all the hard work worth it? You look at your mom and sigh as you realize your tummy has the same bulge over your waist band that she does.
Why is your best friend so skinny? Is it because of her skinny mom? You’re 99% sure she’s allergic to sweat and doesn’t know where the gym is so you decide life is not fair.
And then you check yourself because the color green doesn’t suit you.
How Genetics Play a role on Your Body Type
Body genetics are sort of the pink elephant in the room when it comes to health and fitness goals- you don’t want to admit they matter and you don’t want to sound like you’re making excuses. But you constantly find yourself wondering what you do and don’t have control over.
Simply put, the exact influence of genes on your physique is not absolute; we know they play a role but they do not have to be your fate.
If your parents are obese, categorized as having a Body Mass Index (BMI) of > 30, you run a higher risk of developing obesity, meaning there is a genetic predisposition toward being overweight, making weight management a bit more complicated for some.
A great number of studies on genetics have been done on twins, many estimating the heritability of BMI to be 40-70%. We know that a pair of identical twins who share 100 percent of their genes are more likely to have the same BMI as a pair of fraternal twins who share about 50 percent of their genes.
What’s even more telling is that when identical twins have been raised apart in different environments, they still tend to have similar BMIs.
Along with BMI, we see twins having similarities in skinfold thickness, waist:hip ratio, and waist circumference.
The exact mechanism in which we inherit the susceptibility to distribute fat in certain ways is not clear; some studies have made a neuronal connection, while others have concentrated on genes and enzymes specific to fat stores.
Below are some of the biochemical markers currently being researched in connection to obesity and weight gain:
Genes, Enzymes, Hormones and their effect on Weight Regulation
FTO gene – a nuclear protein connected to BMI, obesity, and type 2 diabetes.
SCD-1 gene – encodes an enzyme that hinders fat burning and promotes fat storage in muscle.
GIRK-4 gene – a gene possibly associated with food regulation and energy expenditure and has been linked to adult-onset obesity in animal studies.
TPP II enzyme – has been shown to stimulate the formation of new fat cells and has been connected to hunger signaling in animal studies.
TRAP enzyme – has been linked to the formation of new fat cells.
Other genes with >20 studies positively associating them with obesity include the ADRB2 gene, the ADRB3 gene, and the PPARG gene.
Genetics and BOdy Weight: Environment, Race, and Ethnicity
As discouraging and frustrating as your unrelenting fat stores can be, there is the theory of the “Thrifty Genotype” to consider, which proposes that those same genes kept your ancestors alive at one point.
In the hunter-gatherer days, those who were predisposed to storing fat in the absence of adequate energy had higher rates of survival than those without genetic advantage.
Unfortunately, today, it is proposed that those same genes lend to the multiple obesity-associated chronic diseases that lead to some of the top causes of death in the United States.
In other words, thanks for your help genes, but you’re really not helping anymore.
Ethnic background has also definitively been tied to your weight status. In the United States, non-Hispanic blacks have the highest prevalence of obesity (38.1%), followed by Hispanics (31.3%), and non-Hispanic whites (27.1%).
Is there a racial genetic component? Researchers are studying links between race and fat stores. For instance, one study found that people of African ancestry possess three genes that may impact BMI and increase tendency toward obesity.
On the other hand, we also know that race, ethnicity, and cultural background influence our environment and daily patterns which greatly impact our food and lifestyle choices.
Although the human genome has remained the same, our world is different. Major changes in energy expenditure and food consumption took place with the onset of the Industrial Revolution, the invention of the automobile, and advances in mass-food production.
What does this all mean? It means there is no one answer and we simply need more research.
Genetics and Taste Preferences
How about the foods you choose to eat? Is there a reason you taste soap when you eat cilantro but your siblings pile it sky high onto their tacos?
Numerous studies show that there is a genetic component to food preferences.
The presence or absence of certain genes has been linked to the preference or aversion of certain foods.
One way genetics influences taste preference is the sensitivity an individual has to bitter compounds in foods: individuals with low taste thresholds for bitter compounds have more food dislikes than those with higher taste thresholds.
The best known of these bitter compounds is PTC, mainly influencing individual’s preference for certain fruits and vegetables.
Why the variation in our taste preferences? One theory is that the ability to identify and reject bitter substances provided our ancestors an evolutionary advantage to help identify bitter plant poisons. To avoid death.
Again, thanks genes, we’re good now.
Genetics and Physical Activity
Ok, now let’s get to the gym. If your mom can pump some serious weight, do you have an upper hand in the gym? If your dad played college ball, does that help your athletic performance?
Twin studies show that up to 90 percent of your baseline muscle strength is hereditary. This is believed to be at least partly due to variations in fiber type.
If you have more slow-twitch (type I) fibers, you may be better able to perform endurance-related activities but have a harder time increasing your muscle mass.
On the other hand, if you have more fast-twitch (type II) fibers, you may build muscle mass more easily but have a tougher time with endurance.
True testing of your muscle fiber constitution requires a muscle biopsy, but if you see an athletic trend in your family, you may be able to figure it out.
How about cardio? Has running always come easy to you while your friends struggle to get past a mile?
Well, you may have more tiny DNA segments called single nucleotide polymorphisms (SNPs). One study showed that individuals who possessed 19 or more improved their cardiovascular fitness three times as much as those with nine or less.
No talented athlete, however, would be half what he or she was without strong bones. They are the foundation that strong muscles are built upon and the framework that determines your mobility. And it’s genetic; bone mineral density (BMD) has a 50-90% heritability rate.
Lean muscle mass, leg extensor strength, and grip strength have all been positively associated with BMD.
But we also know something else. BMD is influenced by good ol’ weight bearing exercise.
Genetics and Body Type
Despite the numerous connections being made between genes and body composition, there have been equally strong connections being made between exercise and body composition.
Exercise can reduce your genetic predisposition of overweight by as much as 40 percent.
Although there is a genetic factor in muscle fiber composition, we know there is an undeniable connection between muscle fiber area and training. Muscle bulk and strength have only a moderate genetic component explaining 30–50% of their growth, leaving the majority to be explained by environmental factors.
This leaves room for physical activity and strength training to improve athleticism, strength, and further increase lean body mass.
Wrapping Up Body Genetics
So what does it all mean? It means that yes, just because obesity runs in your family and you are more prone to a certain body type, it does not mean you have any less control over your own personal actions.
No matter your chromosomal make-up, there is no one gene that can entirely hinder weight loss or muscle growth. These are normal physiological consequences of prolonged daily behaviors such as decreased caloric intake and strength training.
On the flip-side, if you were born with a six-pack, a natural mesomorph, but don’t do the work to maintain this genetic advantage, you too can gain weight and lose lean body mass.
No one is immune to the benefits of a healthy lifestyle or the consequences of lack thereof. If you feel you are struggling more than your friend beside you working the same exact routine, the truth is, you just might be.
But that is all the more reason to turn your attention to the inside, focus on yourself, and create realistic goals and expectations.
It is important to be aware that you are unique and that your body genetics was influenced by Mom and Dad the day you were born, but it is equally important to realize that the decisions you make in young adulthood and beyond are yours alone.
Will your cankles ever go away? Nope. But your belly can. Will your boobs spontaneously go up a cup size? Probably not, but you can put inches on your booty if you work it right.
So look in the mirror, thank your parents, put on your sneakers, and go to the gym. Be the best you can be because that is more than enough.
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