Do our genes matter when it comes to weight loss?
Why metabolic science is so confusing.
Even though a calorie deficit is required for weight loss to occur, there isn’t a one-size-fits-all approach to weight loss.
You’ve probably wondered why some people are able to eat a horse and stay slim while others can gain weight even before they can say the word “cake”.
In all honestly, there aren’t exactly clear answers to why there can be such a disparity between body types and their ability to lose weight, but there are a few things that contribute to their differences.
In this blog I’ll highlight two types of genes scientists have found that differentiate how we exert energy and how that can affect how much weight we lose or gain.
Now as always, I will preface this by saying that research is exactly that, research.
While scientists are able to give us the data they find in their research, its important to note that there are also confounding factors to note when trying to compare yourself to the average statistic so therefore as an individual you may or may not fall perfectly in line with their data, so bear that in mind as you read this.
There are two types of people in the world
Scientist have categorised people into two groups of calorie burners; the ones that tend to ‘burn’ energy easily, called the spendthrift phenotypes and the ones that tend to hold on to the energy they consume called the thrifty phenotypes.
The experiment…
Researchers set out to find out exactly how and why different people spend energy so they round up a bunch of people, stuck them in a room, calculated their energy needs to maintain weight, then starved them and watched what happened.
108 people volunteered to live in a respiratory chamber where they were kept at an energy balance for 24 hours, followed by a period of fasting for 24 hours.
This is what happened…
Those that were identified as thrifters were found to have shown a decline in energy expenditure far more than their counterparts.
Thrifters experienced an average of 11% energy decline whereas the spendthrifts only experienced 4%.
What that might look like in real life is a slowing down of movements and overall lethargy greater in the thrifter group than the spendthrifts.
Interestingly however, during the 24 hours of fasting, both groups were shown to have ‘burned’ the same amount of calories.
Wait, how does that even work you might be asking. If there is a disparity in the energy decline how can energy expenditure be the same?
It appeared as though the thrifters started the fasting phase at a much higher baseline than the spendthrifts since they had burned an average of 124 calories more whilst in maintenance.
So, exactly what is causing the disparity in rate of energy of expenditure between the two groups? The answer lies in the hormones.
While both groups still experienced a decline in energy expenditure, the spendthrifts bodies began releasing their fight or flight hormones (an evolutionary survival tactic designed to keep us alive) more so than the thrifties by 430%.
Hormones like epinephrine are released during moments of stress, designed to help us stay alert. Back when we were hunter gatherers, these would serve to move us into action, find food and feed our families.
When these hormones are released, our airways and blood vessels open up which means we are able to take in more oxygen and nutrients, thus helping us stay alive.
Contrastingly however, those that were identified as thrifty phenotypes downshifted their metabolism, allowing them to hold on their reserved energy, also an evolutionary trait designed to keep us alive.
Evidently, human evolution has developed in a way that allows both phenotypes to survive under starvation; some reserve energy and some become even more alert as a way to fight for survival.
So now that we have established the differences in how we exert energy, this leads us to the next commonly asked question…
How much body fat do we actually need and how much is considered healthy?
It depends, but now that we have a basic understanding of how different phenotypes hold on to their energy, I hope it makes a little more sense to not compare your body to someone else’s.
While there are guidelines as to how much fat is considered healthy, each person is different.
The recommended amount of body for women is anywhere between 19% to 25% and for men 9% to 15%.
Why such differences?
Because what it takes one person to remain lean may not require the same amount of commitment and suckiness as another person.
Takeaways
If you’ve always wondered why you’ve struggled to build muscle * Me: waves hand in the air frantically * or why you find it so hard to remain lean, it’s quite possible you may have to make more adjustments to your training (work smarter not harder), overall energy expenditure (think long walks and house work) and eating habits (considering energy density food rather than volume).
The good news is you can challenge your body type and ‘set point’, it might just take more effort and patience and a really really good strategy. Anyone can gain, lose or maintain weight, its a question of how much of that you can achieve whilst doing so in a sane and safe way that is also sustainable for your body.
Every person is different.
Being healthy isn’t just the absence of disease, it’s also your state of mind so if you have a healthy amount of body fat, don’t suffer from any physical illness but you’re miserable and spend your days counting calories and picking apart your reflection, that’s not health.
Conclusion
It feels like lately I write a lot about body acceptance and compassion. Everyday I can see what people are doing to their bodies to look like filtered versions of other people online.
Because of this, I’m making it my mission to give you the facts without the fluff so that you can determine for yourself what health looks like to you.
So my dear athlete, before I sign off, I’ll leave you with this quote…
“Your best weight is whatever weight you reach when you’re living the healthiest life you can enjoy.”
Comment below if you’ve made some powerful mindset shifts about your body recently, I’d love to hear your thoughts.
References
Tim Hollstein, Alessio Basolo, Takafumi Ando, Susanne B Votruba, Mary Walter, Jonathan Krakoff, Paolo Piaggi, Recharacterizing the Metabolic State of Energy Balance in Thrifty and Spendthrift Phenotypes, The Journal of Clinical Endocrinology & Metabolism, Volume 105, Issue 5, May 2020, Pages 1375–1392, https://doi.org/10.1210/clinem/dgaa098
Weyer, C., Vozarova, B., Ravussin, E. et al. Changes in energy metabolism in response to 48 h of overfeeding and fasting in Caucasians and Pima Indians. Int J Obes 25, 593–600 (2001). https://doi.org/10.1038/sj.ijo.0801610
Martin Reinhardt, Marie S. Thearle, Mostafa Ibrahim, Maximilian G. Hohenadel, Clifton Bogardus, Jonathan Krakoff, Susanne B. Votruba; A Human Thrifty Phenotype Associated With Less Weight Loss During Caloric Restriction. Diabetes 1 August 2015; 64 (8): 2859–2867. https://doi.org/10.2337/db14-1881
