As seen in Psychology Today.
Obesity is a public health problem affecting much of the developed and developing world, as it increases one’s risk of developing type 2 diabetes, liver disease, cardiovascular disease, sleep problems, and a dozens of other chronic conditions that can reduce quality of life and potentially be fatal. In the United States, it is estimated that 42.4% of adults are obese, including 9.2% of whom have severe obesity, and another 30.7% of adults are overweight.
While clinicians should avoid perpetuating a culture that fixates on arbitrary numbers or shames individuals into believing that there is one ideal and often unobtainable body type that they must pursue in order to be healthy, our patients also need to recognize the risks associated with carrying excessive body fat. People come in all sorts of shapes and sizes and there isn’t one type of body composition (consisting of muscle, fat, bone, and water) that is best, but there are ranges that are preferable for optimal health. Clinicians need to drive this point home.
There have been countless studies showing a strong association between the types of metabolic conditions and chronic diseases noted above, but the evidence to support a correlation between excess body fat and neurocognitive disorders has been more limited. However, a new study by Raji and colleagues published in the journal Aging and Disease has found that excess fat does impact brain health. Moreover, it shows that a specific type of fat appears to be strongly associated with cognitive decline and dementia.
Visceral Fat and Subcutaneous Fat
Fat is an essential part of the body, and we need a certain amount of it to store energy, keep us warm, and regulate bodily functions like immune system and metabolism. Fat only becomes problematic when there is too much of it, especially when it accumulates in the abdomen, where it is known as visceral fat (or visceral adipose tissue). It is distinct from subcutaneous fat, which is the type of fat that sits between the skin and muscle.
Though all fat is hormonally active and releases numerous signaling molecules that can lead to inflammation, visceral fat is more active than subcutaneous fat—hence the reason why excessive visceral fat is such a major health concern. Chronic inflammation can disrupt the proper function of the immune system and gastrointestinal tract (see my previous post on the subject here), leading to a host of symptoms like frequent infections, fatigue, and sleep problems. Chronic inflammation can also affect tissue in the central nervous system (CNS), as inflammation can spread into the brain and cause neuroinflammation, leading to symptoms like depression and anxiety, as well as lower brain volumes in some scenarios, as the Aging and Disease paper contends.
Excessive Fat and Alzheimer’s Disease
The Raji study is based on an analysis of 10,001 participants. What the authors found was a clear correlation between increased body fat composition during middle age (one’s 40s and 50s) and reduced volumes of key areas in the brain: the hippocampus, posterior cingulate, and the precuneus, among others. The team focused on these three areas of the brain because they are affected early in the pathological progression of Alzheimer’s disease. They are primarily responsible for the creation and storage of short-term memory, as well as the regulation of mood and emotion. They are also part of the default mode network, which is active when an individual becomes more introspective and less focused on the exterior world.
Study participants who had more adipose tissue, particularly visceral fat, were more likely to experience reductions in volume of these areas of the brain, strongly suggesting greater susceptibility to Alzheimer’s disease. According to the authors, the association between higher visceral fat volume and lower volumes of the specific sections of the CNS noted above was mediated by proinflammatory molecules that cross through the blood brain barrier (BBB) and cause neuroinflammation.
The areas noted above were affected more than other parts of the CNS because they are made up of what is known as gray matter as opposed to white matter. The former is more reliant on the BBB for protection than the latter, which is shielded by an insulating protein known as myelin.
Of note, the team also found that subcutaneous fat had a stronger relationship to lower brain volumes but believe that this relationship is due to the fact that approximately 90% of total body fat is subcutaneous as opposed to visceral. In other words, when sample sizes are the same, visceral adipose tissue produces more inflammation than subcutaneous adipose tissue, but there is nine times more of the latter than the former.
Why This Matters for Psychiatry
Patients with psychiatric disorders are approximately 50% more likely to be obese than the general population. The increased risk does not arise due to genetics or lifestyle alone, as certain psychiatric medications—specifically atypical antipsychotics—can contribute to rapid weight gain. Consequently, we need to consider the downstream effects of these medications.
Beyond that, clinicians need to take a more transcendent view of medicine and recognize the central role that diet, exercise, sleep, and lifestyle choices play in maintaining overall health and wellbeing. Though our field is dedicated to treating mental illnesses and promoting patients’ mental health, the notion that psychiatrists should only concern themselves with what happens above patients’ shoulders and leave the rest to other specialists or generalists is seriously outdated. Chronic inflammation due to obesity or other factors clearly aggravates existing psychiatric symptoms and, as the above study indicates, accelerates neurocognitive decline.
If we want to promote brain health and subjective well-being, we need to consider these factors. As is often the case, an ounce of prevention is worth a pound of cure and clinical psychiatrists are in a unique position to encourage patients to take steps to improve their overall health through better diet, exercise, and other lifestyle interventions.
This blog was written entirely by a human with no assistance from generative AI tools.
Source Image: Towfiqu Barbhuiya/Pexels/Uses with permission