Are You Wearing Your Genes?

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Is obesity genetic?  Or is it caused by our environment (which largely consists of what we eat and what we do, i.e diet and lifestyle)?  The answer is…YES!

Weight status, measured by BMI, typically falls in a bell shaped distribution pattern, with the majority of people falling under the “bell shape” of the curve.  It is normal for there to be people that fall outside of both sides of the bell curve.  There are fewer of them, but that doesn’t mean they are not normal.

(The red curve here is a more recent BMI curve, the black is more historical)

FYI: Morbidity and mortality (risk of illness and death) is higher for people on both sides outside of the bell-more so for the underweight (BMI < 17, 18)

We can easily recognize that there are different body types.  Some are naturally “skinny”, some tend to more fatness, some are small, big, stout, lean…etc. etc.  Different types of obesity have even been defined.

• Type I -excess percentage of body fat noted
• Type II- excess truncal abdominal fat (carrots)
• Type III-excess visceral abdominal fat (apples)
• Type IV- excess glueofemoral fat (pears)

We now know that different genetic patterns correlate with different types of obesity.  (Sidenote-correlation does not MEAN causation, but it does warrant attention)

We can recognize that many of these body types run in families.  This was first reported by Sir Francis Galton in 1894 (over 100 years ago!)

Yet this perception that normal (and healthiest) = thin seems to persist.

Some (rightly) say that families may share genetic material, but they also share environment, diet and lifestyle habits as well.  Twin studies have been helpful in exploring this “confounder”.  Multiple studies have shown a strong correlation between twins and BMI status, with that correlation being stronger in identical twins compared to fraternal twins.

In studies of twins reared together, the genetic contribution to the body-mass index has been estimated to be 64 to 84 percent.

The study of identical twins reared apart is generally considered to be one of the most effective designs for distinguishing the importance of shared genes from that of shared environments. (2), (3)

The participants in the SATSA (Swedish Adoption/Twin Study of Aging) included 93 pairs of identical twins reared apart, 154 pairs of identical twins reared together, 218 pairs of fraternal twins reared apart, and 208 pairs of fraternal twins reared together. Comparable to other twin studies, researchers found that correlation of BMI in identical twins was greater than in fraternal twins (meaning they were more likely to have similar BMI’s) This correlation occurred whether twins were reared together or apart.  No evidence of environmental influence was detected.

In adoption studies, a greater correlation between adoptees and biologic parents is found.  There is some weak influence of adoptive environment on childhood obesity, but this fades by adolescence.

Sibling studies show that full siblings NOT raised together were found to have similar BMI’s.  This was particularly evident in obese siblings.  A similar, but weaker relationship was found in half-siblings.

Research also shows a clear relationship between BMI of parents and that of offspring.  Multiple large family studies show that obese parents produce a greater percentage of obese children.

Environment must have SOME impact on BMI, obesity, and weight-right?  Research supports the fact that it does.  No surprise there!

Soldiers who enlisted in the Danish army between 1925-1942: obesity was present in 1:1000 soldiers.

• After 1942 that incidence began to climb.
• By 1955: obesity rate was 10:1000
• (10 x or 1000% higher in 13 years!)

The Danish population had not really changed its genetic make-up in 13 years, so something in the environment clearly played some role.

Twin studies where twins were overfed identically and did demonstrate correlation in both weight gain and visceral fat gain (in the belly around the internal organs) still demonstrated some discrepancies between twins, so there seems to be some environmental influence.

I think we are all savvy enough to know, that it is not just ONE thing that determines our weight.  Along with other influences (like socioeconomic status, stress exposure and more) genes and environment  interact with each other to impact weight and health in many ways.

In a study looking at dietary fat intake influence on BMI researchers looked at 4 groups of women over a 6-year period.  Those who were

• Overweight with overweight parents
• Overweight with normal weight parents
• Normal weight with obese parents
• Normal weight with normal weight parents

High fat intake correlated with increased BMI only in those who were overweight with overweight parents at baseline.  This group was the only group that appeared more susceptible to weight gain in the presence of high fat intake. (1)

Another military study followed soldiers for a 35-year period.  As dietary fat intake in the group increased, it was followed by increased prevalence of high BMI, but there was no change in the MEDIAN bmi, meaning that just a small subgroup was affected by the higher fat intake).

FYI: The median of a set of numbers is the value separating the higher half from the lower half of a data sample, a population, or a probability distribution. For a data set, it may be thought of as the “middle” value.

As I have stated many times before, obesity is complex…and is not fully understood.  There is no “ONE” obesity gene…in fact there have been 227 possible genetic links to obesity. (4)

The biologic pathways that can influence obesity and that would be influence by genetic differences include:

• Central nervous system
• Food sensing
• Digestion
• Fat cell differentiation
• Insulin signaling
• Lipid (cholesterol, triglycerides) metabolism
• Muscle and liver biology
• Gut microbiome

Recognizing the diverse potential genetic impact on weight (obesity and leanness) reinforces my motto…  “It’s not about your weight, it’s about your well-being”.  Considering  you may have a genetic tendency to be more susceptible to environmental impact is no reason to not take care of your wellbeing.  If you take exquisite care of yourself and focus on living and aging well (following this recipe for optimal health can be a guide)-you will help your genes do what they need to do to help you thrive.  Your weight will optimize.

If you are “doing all the things” and your weight isn’t where you want it…you may need more time.  You may need to accept that you are at your optimal weight.  Only time will tell.  Trying to reach a “target weight” just, well, misses the target.  If you restrict food or over-exercise to lose weight, or force your body out of its optimal zone, your body will take that as a danger signal.  “Warning, this human is trying to starve me to death!  I better slow down my metabolism, hunt for more food, and store every calorie I can! (those stored calories = fat btw…just sayin.)  This can be hard to accept, I know.  You may need to grieve the loss of the “skinny dream”.    But keep taking exquisite care of yourself, honor your body’s signals and needs (hunger, thirst, the need for community, distraction, and security, to name a few).

Accept and love yourself (and others!), enjoy living in a healthy body, whtev.   You are so very worth it.

Mindset Matters Most

Do you feel like you have to “get  back” to “being healthy” after vacation, enjoying summer holidays, or special times?  Do you feel that they are two separate ways of being?  Do you have to give up or deny one to have the other?  Sustaining either(being healthy or having fun) is very difficult if not impossible with that mindset!

Yes, special times are special because they are just that-not the usual, not ordinary.  Why do we often see pursuing the changes and habits we want to establish as WORK, as being HARD, as NOT being fun?  Can they fit in with special and fun times?

This is an opportunity here!  If you can find a way to see your desired way of being (and the effort to become that) as special, as interesting, as fun even-your journey will feel much more effortless and be so much more enjoyable!  And you will be much more likely to follow through.   Give up the idea of having to be perfect. (blech!) That commitment isn’t achievable or sustainable.

Make your choice of what you want, commit to it, plan for it, do it, evaluate it, revise it and do it all over again.  This should be a feel good choice, a choice you are excited about, even if you have some trepidation or if your confidence isn’t 100%.

Accept mistakes you make-they are learning opportunities.  (Bad days make great data!)

Coaches Corner:

Listen to how you talk about your goals, the behaviors you want to adopt or change.  Do you use phrases like “I’m not allowed to eat that”, “have to do this” “supposed to”, good or bad, right/wrong.  Watch for those absolutes and try to modify them.  Consider using words like “choose to”, “I am”, “I do”,” this is helpful, impactful, meaningful”,” I am making progress”!

Watch for how your words affect your energy and your outlook about the behaviors and habits you want to establish.  You may find yourself rephrasing often.  That’s ok, that’s great actually!  It means you are noticing and becoming self-aware!  Yay you.

 

 

References for this issue

1. Thorkild I.A. Sørensen,The genetics of obesity,Metabolism,Volume 44,Supplement 3,1995,Pages 4-6,ISSN 00260495,https://doi.org/10.1016/0026-0495(95)90310-0.

2. Body Mass Index of Twins Reared Apart, DOI: 10.1056/NEJM199005243222102

3. The genetic and environmental influences on childhood obesity: a systematic review of twin and adoption studies K Silventoinen1,2, B Rokholm3 , J Kaprio,2,4,5 and TIA Sørensen3 1 Department of Sociology, Population Research Unit, University of H

4. Pigeyre M, Yazdi FT, Kaur Y, Meyre D. Recent progress in genetics, epigenetics and metagenomics unveils the pathophysiology of human obesity. Clin Sci (Lond). 2016 Jun 1;130(12):943-86. doi: 10.1042/CS20160136. PMID: 27154742.