This is a tough question that you may be inclined to answer without giving it it’s due consideration. Many people seem to think of it as if there’s an ‘Obese button’ or ‘Not obese button’ and if someone’s obese it is their conscious decision. Realistically, it’s not how it works. For starters, if you selected 100 people at random and gave them the option, surely almost everyone would press ‘Not obese’. People know about the potential health risks and social stigma that come along with being obese, so few, if any, would consciously choose to be obese. However, it is a different kind of decision-making.

Throughout our lives, each day we have a continuous series of choices to pick certain foods over others. In addition, we decide on certain behaviours over others. Over time, it could be the cumulative effect of these many individual choices that causes someone to become obese. Although this seems to be 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.

The study involved subjects under 24/7 supervision to ensure protocol adherence. Each bar represents an individual, with the bar height indicating weight gain in response to a 1000 calorie surplus. Despite uniform calorie intake, there are significant variations in weight gain, potentially attributed to factors like genetic differences in metabolism.

A subsequent 2018 study further reveals variations in resting calorie burn among individuals, emphasising the diverse
responses to calorie surplus.

The person on the right burns about 150 calories than metabolic equations predict, while the person on the left would burn 250 calories less. In other words, if no one exercised, the person on the right would still burn 400 calories more per day than the person on the left.

Referring back to the buttons, a small McDonald’s fries has about 200 calories and a large one has about 600. All else being equal, that’s a 400-calorie surplus if you choose the large.

However, the person on the right also burns 400 calories more, so through no action of their own, they could choose the large every time and their net caloric balance would be exactly the same as the other person who chooses the small. Keep in mind that this only considers Resting Energy Expenditure – the number of calories burned at rest.

People also burn calories through exercise, the thermic effect of food, and non-exercise activity thermogenesis (NEAT).

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

NEAT – the calories a person burns from daily activities that aren’t exercise (i.e. fidgeting, tapping your feet, 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. Hence, anyone who has 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.

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, yet still 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 realising 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.

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 and a low-fat meal.

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(grey 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. These two genetic factors however are not the only biological factors that play a role.

Whether or not you take 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.

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 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?

The spike wasn’t 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 lifestyle factors, like how much sleep you get and while it may be easy to tell people to just get more sleep, that isn’t always feasible, depending on work, and other responsibilities.

In fact, a 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. Another meta-analysis from the same year found that depression was also predictive of obesity risk.

So, “Is Obesity a Choice?”

The answer is NO. At least not in all cases, and certainly not in the simplistic sense. There’s too much of an influence from genetics and environment to shift the blame solely on the individual.

Of course, that doesn’t mean that no one has control over their health and their body weight. 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, the ‘Is obesity a choice’ comes back to semantics. Perhaps what choice means differs slightly from one person to the other. The best argument for it being a choice would be that it is a complex series of choices intertwined with many other complex contributing factors.



Written by: Luca Theuma


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