Is Obesity A Choice? (Science Explained)

This is a tough question that you may be inclined to answer without giving it it’s due consideration. Many people seem to think about obesity as if there's an ‘Obese button’ on the left and a ‘Not Obese’ button on the right. If someone’s obese, it’s because they made a conscious decision to press the obese button.

I don’t think that’s how it works. For starters, if you selected 100 people at random and gave them the option, surely almost everyone would press the ‘Not Obese’ button. People know about the potential health risks and social stigma that can come with being obese, so few, if any, would consciously choose to be obese in this simplistic sense.

As we think it through, maybe things look more like a different kind of decision-making.

Throughout our lives, each day we have this continuous series of choices to pick certain foods over others, like whether to order fried chicken or grilled chicken, regular coke or diet coke, a small fries or super-sized fries. In addition, we decide on certain behaviors over others, like whether to get up and exercise or stay on the couch.

Over time, maybe it’s the cumulative effect of these many individual choices that causes someone to become obese.

Although I do think this is a bit closer to reality, even this analogy is still very incomplete.

Consider this graph taken from a 1990 study where 24 subjects were overfed by a thousand calories per day for about three months.

Since all the subjects were under 24/7 supervision by the research staff, we can be confident that they were actually following the protocol. Each one of the bars represents a single person and the height of the bar represents how much weight they gained in response to the 1000 calorie surplus.

Despite each person eating the same extra 1000 calories per day, note how the person on the left only gained 10 pounds, while the person on the right gained an extra 30 pounds. This could be due to a number of factors, but a big one is genetic differences in metabolism.

Looking at this later study from 2018, we can see that just like there are large differences in weight gain, there are also differences in how many calories people burn at rest, simply sitting on the couch doing nothing at all.

The lucky person on the right burns about 150 calories more than metabolic equations predict, while the person on the left would burn 250 calories less than metabolic equations predict.

In other words, if none of these people exercised at all, the person on the right would still burn about 400 calories more per day than the person on the left.

Going back to the buttons, a small fries from McDonald’s has about 200 calories and a super-sized fries has about 600 calories. All else being equal, that’s a 400-calorie surplus if you choose to supersize.

However, the person on the right also burns 400 calories more, so through no action of their own, they could choose to supersize every time and their net caloric balance would be exactly the same as the other person who chooses the small fries.

Keep in mind that this only considers Resting Energy Expenditure - the number of calories you burn at rest.

People also burn calories through exercise, the thermic effect of food, and something called non-exercise activity thermogenesis or NEAT.

The NEAT component of metabolism can vary dramatically between individuals, even more than resting energy expenditure.

NEAT refers to the calories you burn from daily activities that aren’t actual exercise, including stuff like fidgeting, tapping your feet, squirming in a chair, etc. Even though you can somewhat modify your NEAT levels by making an extra effort to move around a bit more throughout the day, the NEAT is still largely subconsciously regulated in the brain, and is dynamic.This means that if you have a genetic predisposition for low NEAT, you aren’t very hyperactive and you don’t fidget much.

Let’s say you try to force yourself to fidget more. In many cases, your brain would simply find a way to lower NEAT someplace else. This indicates that NEAT is, to a significant degree, outside of your control. In addition, NEAT levels can differ enormously between individuals.

Have a look at this study from Levine and Colleagues where researchers overfed participants by a thousand calories per day. After eight weeks, they found that NEAT levels ranged from -98 (that is, they actually moved around less) to +692 calories per day.

This means that while both of these subjects ate an extra thousand calories per day, one person quite literally fidgeted off about 700 of those extra thousand. Since the other person actually fidgeted less, their body had to deal with all those extra 1000 calories eaten.

Clearly then, anyone who’s been genetically blessed with a high resting metabolic rate and high NEAT levels can choose to press the junk food button many more times and still maintain a lower body weight, compared to someone who’s not metabolically gifted. This conclusion aligns with our everyday experience.

We all know someone who can eat whatever they want and remain almost inexplicably thin, and we all know someone who’s tried every diet book on the shelves, yet remains overweight.

Most people would be quick to praise the thin person for their discipline and critique the overweight person for simply lacking willpower and making the wrong choices, not realizing the many baseline genetic factors that could be making it very easy for the thin person to stay thin and making it very hard for the overweight person to lose any weight at all.

But there’s more to consider here than just metabolism. There’s yet another big influencing factor: Hunger variations.

Research shows that in response to dieting, some people simply experience more hunger than others. While many dieters feel like they’re constantly fighting their body’s urge to eat more, others feel more normal hunger, where it’s low after meals and picks up as it gets closer to meal time.

Consider this hunger study from 2013 which looked at the difference between eating a high-fat meal (yellow) and a low-fat meal (green).

It turns out that individuals fed a high-fat meal and a low-fat meal were able to suppress hunger very well on average. However, when that average trend was split up into individual subjects, you suddenly see this huge disparity between individuals.

Some people were still quite hungry after eating the meal (orange arrow), while others felt very full (gray arrow).

Since hunger is what naturally drives food intake for most people, we once again see that, compared to someone who feels full, someone who still feels very hungry after a meal will have a harder time resisting food.

We’ve covered two genetic factors explaining why weight gain happens to some people more easily than others, even given the same food and exercise choices. But there are still so many other biological factors that can play a role. Whether or not you take certain medications that can increase appetite and water retention is but one variable.

There are also neuroendocrine conditions that can impact weight gain through hormones and metabolism. Then there are pregnancy and menopause, which have hormonal and metabolic impacts, and physical disabilities, which makes burning calories through NEAT and exercise more challenging.

Of course, all this doesn’t mean that ‘calories in-calories out’ only works for some people. It’s a simple fact that obesity results from eating more calories than you burn. Tightly controlled metabolic experiments repeatedly confirm that caloric intake is the driver of both fat loss and fat gain.

This means that anyone who is obese got obese by eating in a sustained caloric surplus over time.

It’s just that, for reasons that are beyond their choosing, avoiding that sustained surplus is so much harder for some people than it is for others. This is why I think it’s incorrect to reduce all of these factors down to a simple choice to be obese or not.

If becoming obese was indeed a simple choice, why would obesity rates suddenly start trending up in the 1970s? Did people just suddenly start choosing to be obese? Or is there yet another layer to this?

I don’t think that the spike was due to more people choosing to be obese, but rather resulted from high-calorie foods becoming so much more readily available for cheaper prices. This meant that more people had more access to delicious highly processed calorie-dense foods.

This of course leads us into the whole other side of this obesity discussion: Environmental Factors.

Entirely separate from the genetic and biological factors that we just went through, there are also environmental factors that can impact your susceptibility to obesity.

Environmental factors include the food environment, where apart from the spike in availability, we also see better flashier marketing for high-calorie foods that promote overconsumption and large portion sizes.

There’s also the fact that junk food tends to be cheaper, meaning it’s more accessible for people of lower economic incomes. Then there are social factors like the type of diet your family and friends eat, which can make it a lot harder. In the case of dependents like children, it’s virtually impossible to make so-called good choices.

Then there are the Lifestyle Factors, like how much sleep you get. And while it may be tempting to tell people to just get more sleep, that isn’t always feasible, depending on work, and other responsibilities.

In fact, this 2017 meta-analysis found that night-shift work was associated with a 23% higher risk of being overweight.

A 2019 meta–analysis found a dose-response relationship between sleep duration and obesity risk. Less sleep meant more risk of being obese, with 7-8 hours being the sweet spot on average.

Of course, we can’t forget the impact of Psychological Factors, like stress and depression, on our weight gain and retention ( Note the 2010 meta-analysis of 14 studies shown below).

And this other meta-analysis from the same year found that depression was also predictive of obesity risk.

At this point, let's return to the original question: “Is obesity a choice?”

I think the answer is NO. At least not in all cases, and certainly not in the simplistic sense. There’s just too much of an influence from genetics and environment to shift the blame entirely on the individual for their circumstance.

Of course, that doesn’t mean that no one has any control over their health and their body weight.

Clearly, if people want to lose weight, even if there are many factors working against them, such as low metabolic rate and higher hunger, it’s still possible to lose weight if you sustain a caloric deficit over time.

Ultimately though, I think the “Is obesity a choice” question comes back to semantics. Perhaps what I mean by “choice” is slightly different from what you mean by choice. I think that if you did want to argue that it is a choice in some sense, I think the best you could do is say that it’s a complex series of choices intertwined with many other complex contributing factors.

As many people in the health and fitness space think, I also believe that we should make an effort to be more understanding of these factors and extend more compassion toward people who are struggling, rather than making assumptions about their choices and their characteristics.

Instead of blaming them for their circumstance, maybe we could focus on pointing them in the right direction with good sustainable nutrition advice when they ask for it.

As I clue up here, I want to give a quick shoutout to Dr. Mike Israetel for the button analogy. I first heard that from him and I thought it was great. I’ll also go ahead and link all the articles that I referenced in this blog down below.

If you would like to further explore the topic in video format, a summed-up video of this blog is available on my YouTube channel.

On that note, I’ll end here by saying thank you so much for your interest in this subject! I’ll look forward to digging into another topic with you here in the next blog.

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