Waist Circumference, Cognitive Decline, Alzheimer’s and Dementia


by Nils Osmar. May 24, 2022 – Medical disclaimer

According to a 2013 study entitled “The emerging role of dietary fructose in obesity and cognitive decline“, sugar consumption, body weight, obesity, waist circumference and Alzheimer’s are interconnected.

A larger waist circumference (caused by the accumulation of abdominal fat) is a warning sign that we may be headed in a dangerous direction. But interestingly, having a body fat percentage that’s too low is associated with dangers also.

From the study (emphases are mine):

  • “Obesity is a global health issue that has reached epidemic proportions. Greater than 60% of adults living in the U.S. and Europe are obese (body mass index (BMI) ≥30 kg/m2)…
  • “Over the last three decades, the incidence of global diabetes has more than doubled, with nearly 1 in 10 adults affected worldwide …
  • “Recent studies indicate that both obesity and T2D are associated with cognitive decline. Not only does midlife obesity increase the risk of developing late-life dementia, but also lower cognitive performance earlier in life is itself a risk factor for dementia later in life…
  • “Although several factors, such as a lack of exercise, are likely contributors to the rising trend in obesity, increases in its prevalence are directly attributable to excessive caloric intake…
  • “In addition, there is now strong evidence that excessive consumption of added sugars (sucrose and high-fructose corn syrup (HFCS)), contributes to rising obesity and diabetes rates…
  • “In 2005, Jeong et al. examined the association between obesity and cognition using data from a community study of South Korean adults (≥ 65 years). Cognitive function was examined using the Korean Mini-Mental State Examination, and obesity using BMI and waist circumference, as measured at the level midway between the lower rib margin and the iliac crest…
  • Obesity (BMI ≥ 25 kg/m2) and poor cognitive performance were associated with above normal waist circumference, and poor cognitive performance was negatively associated with overweight (BMI, 23-25 kg/m2) and normal waist circumference…”

Being underweight also increases risk

Being overweight is an established risk factor for Alzheimer’s. But being underweight is associated with similar dangers, according to an article published in the Lancet Diabetes and Endocrinology journal. From the study:

Being underweight in middle age and old age carries an increased risk of dementia over two decades. 

A Guardian article called “Underweight people face significantly higher risk of dementia, study suggests“, elaborates on this point

People who are underweight in middle-age – or even on the low side of normal weight – run a significantly higher risk of dementia as they get older… At highest risk… are middle-aged people with a BMI [body mass index] lower than 20… These people have a 34% higher chance of dementia as they age than those with a BMI of 20 to just below 25, which this study classes as healthy weight.”

So is it better to be overweight than underweight? Is obesity actually protective? Quoting again from the Guardian article:

Lead author Dr Nawab Qizilbash from Oxon Epidemiology told the Guardian that the message from the study was not that it was OK to be overweight or obese in middle-age. “Even if there were to be a protective effect in dementia, you may not live long enough to benefit because you are at higher risk from other conditions,” he said.

But it is clear that just as we can be too heavy, we can be too lean, from a brain health point of view.

Sorting it all out

The results of the studies tend to seesaw back and forth. But it’s clear that being obese is the greater danger. From a 2o21 article entitled “Alzheimer’s disease: obesity may worsen its effects – new research”

Being overweight increases the risk of many serious health conditions, including strokes, cancer, diabetes and hypertension.

Less well known, perhaps, is the link between being overweight or obese and the health of our brain. Research has shown that a higher body mass index and mid-life obesity are both linked to increased risk of dementia. Some evidence also indicates that obesity and Alzheimer’s disease cause similar brain dysfunctions.

Our latest research has now shown that being overweight or obese negatively affects brain health, especially in the regions most vulnerable to the effects of Alzheimer’s disease. This could potentially exacerbate symptoms of Alzheimer’s disease should it develop.

Our study looked at 57 people who were healthy and had no sign of Alzheimer’s, 68 patients who had mild cognitive impairment but could still function normally in everyday life, and 47 patients with a clinical diagnosis of Alzheimer’s dementia….

Our findings showed that in overweight or obese people who had no or mild cognitive impairment, the more excess weight they carried, the greater their levels of brain cell loss and the lower their brain blood flow. We also found some damage to fibres that connect brain cells. All of these changes affect mental functions, including how well we remember things and our ability to do everyday tasks.

Are hyper-lean celebrities healthy?

One prominent personality in the world of health podcasts and anti-aging is Ben Greenfield. Greenfield, who is 41 in 2022, is just over 5% body fat. Here’s a recent photo he shared on Facebook, and a test verifying that his % body fat is 5.1.

I like Greenfield and have learned helpful things from his podcasts. But when I look at his recent videos, I have two reactions.

My first reaction is usually that he looks great, strong and flexible. I admire the work that he puts into staying lean and strong. He also seems mentally sharp and clear.

My second reaction is that I’m afraid that people who follow in his footsteps may be setting themselves up for future health problems. We’re all aware of unrealistic expectations that are placed on women to become and stay extremely lean – even emaciated – even at the expense of health (which can feed into issues such as anorexia and bulimia). Creating similar expectations, and promoting very low body fat as “healthy and life extending”, could be problematic for both sexes.

I don’t mention Greenfield to put him down, but to question the notion that having body fat that low is necessarily desirable. From a brain health perspective at least, this may not a healthy direction to be going.

Summing up

  • Obesity and the consumption of large amounts of sugar (including both sucrose and fructose) are not the only causes of Alzheimer’s and other forms of dementia. But they are clearly related, and they are factors we are able to do something about. We may feel a “craving” to eat more sugar (or more calories in any form) than we need to maintain health), but nothing is compelling us to act out our addictive cravings.
  • Staying at a healthy weight (not too lean; not too fat) takes work.
  • It’s important, in my estimation, not to buy the notion, currently being promoted in the mainstream media, that “it’s too hard, and it’s all genetic anyway, diets don’t work, we can’t do anything about it anyway, being obese is an “identity”, it’s bad to talk about it, so we should just stop thinking about it.”
  • Fat shaming is a real phenomenon and is not helpful. It’s categorically different, though, from pointing out the health problems associated both with obesity and with being underweight.
  • From the perspective of preventing dementia, we do need to stay aware of our weight and percentage of body fat.
  • But again, from a brain health perspective at least, having too little fat can be as problematic as having too much.
  • In my opinion, rather than focusing on stripping away as much body fat as we can, a better course would be to just focus on building muscle and maintaining a healthy weight.

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