The Relationship Between Obesity And Mental Health

The relationship between obesity and mental health is complicated, but in this article I take a look at how being overweight can negatively impact your mental health.

Information On BMI (Body Mass Index)
How Bad Is Fat?
Relationship Of Obesity To Mental Health
Infection And Obesity
Environmental Factors In Obesity
Endocrine-Disrupting Chemicals


How is it possible that we know we “should eat less and move more”, but we still gain weight?

Why is it that all manner of fad diets come and go, but we still gain weight?

Why is it that people who actually manage to lose some weight, gain it back?

"Roughly 90 percent of people who lose a lot of weight eventually regain just about all of it." (University of Michigan Health)

I’ll tell you why.

There’s an underlying, unaddressed problem. That problem is mental health.

The relationship between obesity and mental health
The relationship between obesity and mental health

Until you tackle that problem, you’re just shouting at someone with a broken leg to “run it off”.

Many countries around the world have an obesity crisis. Let’s look at the data for two countries I’m familiar with, America and the UK….

USA vs UK obesity and overweight statistics.
Obesity In The USA and UK.
Sources: USA: 2019 NHANES report, UK: 2019 HSE report.

I’m using the “gold medal” comparison because the Olympic Games in Tokyo is drawing to a close. I therefore award “gold” to the USA and “silver” to the UK (“Great Britain”).

It’s really more like a “photo finish” though, because the difference between having 66% of your adult population being overweight, obese or severely obese (also known as “morbidly obese”) and 64% is not really significant, at least not to my mind.

I find it ironic that athletes representing the USA and Great Britain are doing well in the Olympics when the “average” American or Brit is watching on TV and two thirds of them are overweight!

Information On BMI (Body Mass Index)

BMI Information:
The standard measurement for defining whether people are a “normal” weight or not is to calculate their Body Mass Index (BMI). Both reports listed above use the BMI, so we can compare between the two countries.

Is the BMI valid? For most people the BMI is a good gauge of whether or not they’re overweight. Yes, it’s not infallible. People who have a lot of muscle can have a high BMI due to their muscle mass and not be carrying a lot of fat and therefore not be “overweight” or “obese”. However, most people don’t fall into that category.

Calculating your BMI To calculate your BMI you either divide the weight in pounds (lb) by height in inches (in) squared, then multiplying by a conversion factor of 703 or divide the weight in kilograms by their height in metres squared.

Alternatives to BMI An alternative to BMI is “waist to height” measure, where your waist circumference should be less than half your height. So a 6-foot man (72-inches) should have a waist circumference of less than 36 inches, and a 5-foot-4 woman (64 inches) should have a waist circumference of less than 32 inches. It’s thought that abdominal fat may be more unhealthy than fat stored elsewhere in the body, so some people prefer this measurement.

How Bad Is Fat?

The problem is that most people think “fat” is pretty harmless. Yes, it sits on our hips or stomach and slows us down a bit so we can’t run like Olympic athletes, but it’s not actually that bad, is it?

Well, the first point is that excess fat makes us more prone to heart disease, stroke and diabetes in the long run, and those are some of the biggest killers in both the USA and UK, so being overweight or obese is definitely not “harmless”.

But, the story gets worse for anyone partial to calorie-laden drinks and foods.

Recent scientific evidence has shown that fat is not metabolically inactive. It doesn’t just sit there on your hips or beer belly like a pound of butter. It actually affects your internal workings, very negatively.

Adipose tissue is now known to release adipokines, including pro-inflammatory cytokines, small signalling molecules that tell your body something is wrong. It’s these molecules that are thought to make your body less sensitive to insulin, which eventually results in type 2 diabetes, and play a role in heart disease.

Lard vs Cafeteria Diet

Interestingly, it’s not just “fat” per se which is the problem. Rats fed a “cafeteria diet” (“animals are allowed free access to standard chow and water while concurrently offered highly palatable, energy dense, unhealthy human foods ad libitum“) fared much worse when compared to those fed a “lard” diet and controls.

They got fatter and had worse glucose responses:

"Body weight increased dramatically and remained significantly elevated in CAF-fed rats compared to all other diets. Glucose- and insulin-tolerance tests revealed that hyperinsulinemia, hyperglycemia, and glucose intolerance were exaggerated in the CAF-fed rats compared to controls and HFD-fed rats". 

They had higher levels of inflammation:

"Although both high fat diets resulted in increased adiposity and hepatosteatosis, CAF-fed rats displayed remarkable inflammation in white fat, brown fat and liver compared to HFD and controls". 

Which the researchers called a model for studying obesity and obesity-related disease states:

"In sum, the CAF provided a robust model of human metabolic syndrome compared to traditional lard-based HFD, creating a phenotype of exaggerated obesity with glucose intolerance and inflammation. This model provides a unique platform to study the biochemical, genomic and physiological mechanisms of obesity and obesity-related disease states that are pandemic in western civilization today".

It appears that the “lard” diet for obesity in mice is out, and the “cafeteria” diet is in.

In a different study, the effect of a “lard” diet in mice (50% of total energy from lard) was compared to a diet high in fish oils (50% of total energy from fish oils). The inflammation seen in the “lard” diet mice was reduced in those eating the fish oil diet and they didn’t gain weight:

"the HF-FO group did not present increased body mass, adiposity or glucose intolerance. In this group, insulin signaling, macrophage infiltration and inflammation were reduced in WAT in comparison with the HF-L group".

Relationship Of Obesity To Mental Health

Unfortunately, pro-inflammatory cytokines reach every part of the body through the bloodstream. Over the past few decades, it’s been shown that pro-inflammatory cytokines cross the blood brain barrier.

Furthermore, they seem to initiate mental health symptoms similar to depression, fibromyalgia and chronic fatigue.

"Indeed, the newest findings of cytokine actions in the brain offer some of the first clues about the pathophysiology of certain mental health disorders, including depression".

When an organism gets sick, one of the things they do is exhibit depression-like symptoms such as a loss of appetite, sleepiness, social withdrawal, fever, aching joints and fatigue.

A normal infection would naturally generate pro-inflammatory cytokines and such a depression-like state, but only for a short duration while the infection was being fought off.

However, the production of pro-inflammatory cytokines by adipose tissue seems to generate low-level amounts of pro-inflammatory cytokines over a long period of time, akin to having a long-term, low-level illness. Presumably that has a dampening effect on the brain similar to chronic, low-grade depression.

So, ultimately, it could be that the two-thirds of adults living in the UK and USA who are overweight or obese could be generating their own low-grade “chronic illness” state which negatively affects their mental health.

"Cytokine-induced sickness behavior was first described in the literature in 1995. It shares symptoms with fibromyalgia, such as fever, fatigue, pain, anorexia, and irritability. Immunoneuropsychiatric (INP) concepts were first introduced in the study of the pathophysiology of major depression".

"The study of cytokine involvement in the pathophysiology of other neuropsychiatric and metabolic disorders, such as anxiety disorders, bipolar disorder, schizophrenia, headaches, epilepsy, dementia, and delirium, is also rapidly gaining momentum".

There are other issues with cytokines in the brain such as reducing the feedback mechanism involved in signalling satiety.

In overweight people the hormone leptin is produced as normal by fat tissue, but the brain seems to stop being sensitive to it. This is called “leptin resistance” and it means hunger is not switched off and we no longer reduce our food intake as we would if we were sensitive to leptin levels.

"Indeed, commensurate with their large adipose mass, obese individuals exhibit elevated circulating leptin concentrations relative to lean subjects, and these elevated leptin concentrations (obviously) fail to return body adiposity to within the normal range." 

If we can no longer tell we’re full, we’re likely to overeat more and stay overweight / obese. There are also studies that show cognitive impacts from cytokines in the brain, which may influence our ability to decide what we’re going to do about losing weight.

"Through their effects on neurotransmitter systems, cytokines impact neurocircuits in the brain including the basal ganglia and anterior cingulate cortex, leading to significant changes in motor activity and motivation as well as anxiety, arousal, and alarm."

"Chronic activation of this innate behavioral and immune response may lead to depression and anxiety disorders in vulnerable individuals."
(my emphasis in bold)

Overall, the picture is one of a negative cycle starting with gaining weight, which causes changes in the brain that make gaining more weight more likely.

I haven’t even begun to touch on the addictive properties of processed food, which can cause brain changes that are similar to that seen in people with addictions.

Infection And Obesity

There’s also evidence that infection can contribute to obesity. The adenovirus AD-36 has been implicated in obesity, with higher levels of AD-36 antibodies more likely to be found in overweight people.

Recent evidence on animal and human adenoviruses suggests that these adenoviruses may infect adipocytes to alter enzymes and transcription factors resulting in accumulation of triglycerides and differentiation of preadipocytes into mature adipocytes. The E4orf1 gene of Ad-36 has been shown to be responsible for the adipogenic effect. ( source )

The adenovirus, AD-36 was found in 30% of obese humans, but only 11% of non-obese humans:

Ad-36 has been studied the most and is the only human adenovirus to date that has been linked with human obesity. Ad-36 causes obesity in chickens, mice, rats, and monkeys and was present in 30% of obese humans and 11% of non-obese humans. In twins discordant for infection with Ad-36, the infected twins were heavier and fatter than their co-twins. ( source )

No wonder it’s so hard to lose weight and keep it off!

So, what’s the solution?

I believe EpiCentering for Weight Loss will help people lose weight in a natural, drug-free way and keep it off. I’ll be creating this program shortly. Please stay tuned to this website, or follow me on Instagram or Facebook using the links below.

Oh, and just as a “kicker”, the reason it’s almost impossible to keep weight off is because the body makes adjustments to compensate for the weight loss, especially if it’s rapid. Of course, most people aren’t content to lose a pound or two of fat per week, and look for strategies to lose weight rapidly.

"Crash dieting, starving or fasting – eating too few kilojoules encourages the body to slow the metabolism to conserve energy. BMR can drop by up to 15 per cent and if lean muscle tissue is also lost, this further reduces BMR."
Department of Health, State Government of Victoria, Australia

These are epigenetic weight-loss changes the body makes in response to changes you make to your food intake. The body believes it’s entered a starvation phase, and cuts the caloric requirements accordingly.

Epigenetics is one of the reasons for the naming of my program. When you live mindfully, knowing that everything you do (and don’t do), will result in changes to how you think, act and feel over the next minutes, hours, days and years, you are empowered to make better decisions. That’s EpiCentering.

Not only can epigenetics change your patterns of gene expression, but they could potentially affect your offspring too…

"... a demonstration in humans that a mother’s nutritional status at the time of conception can influence her child’s epigenome, with likely lifelong implications".

Environmental Factors In Obesity

It’s interesting that people gain weight which triggers cytokine release and inflammation. That inflammation may then lead to mental health changes which may make over-eating more likely. But what triggers people to over-eat in the first place?

Obviously there are likely to be several reasons, such as parental eating habits, a sedentary lifestyle and the availability of high-calorie snacks and desserts. However, one very interesting study showed that it’s not just humans getting fatter, the animals around us do too.

Surprisingly, we find that over the past several decades, average mid-life body weights have risen among primates and rodents living in research colonies, as well as among feral rodents and domestic dogs and cats. ( source )

The researchers looked at “eight species living with or around humans in industrialized societies” and found that for all of them the trend of bodyweight increased over time.

How is that possible? Is it that our scraps are more fattening? If so, why would animals not just eat until they were full? Something is throwing off their internal sense of homeostasis. Or are there environmental toxicants in the environment which contribute to obesity?

Endocrine-Disrupting Chemicals

The concept of environmental chemicals which pre-dispose people to obesity is gathering traction. See this 2021 report

The environmental obesogen model holds that exposure to obesogens elicits a predisposition to obesity and that such exposures may be an important yet overlooked factor in the obesity pandemic. Effects produced by EDCs and obesogen exposure may be passed to subsequent, unexposed generations.

Note the possibility of these chemicals being passed on to future generations, the mechanism for which would be epigenetics.

If these chemicals are present in the environment we ingest them, breathe them in or absorb them via our skin. Once inside our bodies they may disrupt neurotransmitter or hormone signalling such that we are predisposed to overeat and gain weight.


The relationship between obesity and mental health seems to be mediated by low-level, chronic inflammation.

Fat tissue releases pro-inflammatory cytokines which generate low-level inflammation throughout the body.

These cytokines also cross the blood-brain barrier and affect the brain, leading to mental health issues such as depression and anxiety.

It’s possible that environmental chemicals may be partly responsible for weight gain due to animal species living in proximity to humans gaining weight too.

Neil Shearing, Ph.D.