Why big bellies could mean big trouble for brain function in later life

Previously on this site I have presented evidence that the traditional way of assessing body weight ” the body mass index (BMI) ” is pretty useless as a marker for health. Part of the explanation for this lies in the fact that the BMI tells us nothing about the composition of the body. Neither does it tell us where any surplus weight is distributed. This is important because there is now a mass of evidence which links fat distributed around the midriff (abdominal obesity) with an increased risk of conditions such as cardiovascular disease and diabetes.

This week saw the publication of a study which suggests that having excess weight around one’s middle may be a risk factor for dementia too.

The study in question was published on-line in the journal Neurology. In this study, a measurement known as the ‘sagittal abdominal diameter’ (‘SAD’) was used to assess the extent of abdominal obesity (SAD is basically the distance between the front of the belly through to the back). Specifically, more than 6500 individuals had their SADs measured over a 9-year period (1964-1973). The presence of dementia was assessed an average of 36 years later. The relationship between individuals’ SAD measurements and risk of dementia was assessed, after accounting for so-called confounding factors such as age, sex and the presence of conditions such as high blood pressure, diabetes and cardiovascular disease.

The results of this study showed that:

Individuals with the highest SAD measurements were at a 272 per cent (almost 3-fold) increased risk of dementia compared to those with the lowest SADs.

In further analysis, the researchers took into account individuals’ BMI readings as well. Individuals with a high SAD will tend to have relatively high BMIs too. Taking BMIs into consideration helps to determine more accurately whether the link (if any) between SAD and dementia risk.

Having accounted for BMI measurement, the researchers found that:

Individuals with the highest SAD scores were at a 92 per cent increased risk of dementia.

In individuals with ‘normal’ weight (BMI of 18.5 ” 24.9), those with a high SAD measurement (> 25 cm) were not found to be at a statistically significant increased risk of dementia compared to those with a low SAD measurement (< 25 cm). Overall, what this study suggests is that abdominal obesity is linked with an increased risk of dementia. It's perhaps worth considering the mechanisms that might explain such an association. Some of the explanation may lie in the fact that increased abdominal size is often associated with metabolic syndrome. Previous research has linked metabolic syndrome with an increased risk of stroke " a condition which can lead directly to dementia (sometimes as a result of multiple strokes in which case the dementia is referred to as 'multi-infarct dementia'). Individuals with metabolic syndrome typically exhibit a degree of 'impaired glucose metabolism' (which essentially means they have difficulty keeping glucose levels controlled in the bloodstream). Impaired glucose tolerance (IGT) can ultimately lead to type 2 diabetes. Both IGT and type 2 diabetes have been linked with impaired brain function in later life [2]. A number of mechanisms have been postulated for how IGT and type 2 diabetes may increased dementia risk, including an increased tendency to inflammation as well as 'oxidative stress' (damage wreaked by substances known as 'free radicals') [3]. A key substance to the development of dementia may be the hormone insulin. In one study, individuals given insulin intravenously experienced a rise in the body levels of a protein known as 'amyloid beta' [4]. The significance of this? - Amyloid beta is the prime constituent of the 'plaques' found in the brains of individuals suffering from Alzheimer's disease. The long and short of all this research seems to be this: if you want to do what you can to help preserve your mental faculties as you age, it makes sense to take steps to keep blood sugar and insulin levels under control. For most of us, that will mean a diet relatively low in blood sugar destabilising carbs including many starchy staples bread, potato, rice, pasta and breakfast cereals.

1. Whitmer RA, et al. Central obesity and increased risk of dementia more than three decades later. Neurology 2008 [Epub 26 March 2008]

2. Fisman EZ, Tenenbaum A (eds). Impaired glucose metabolism and cerebrovascular diseases. In Cardiovascular Diabetology, Metabolic and Inflammatory Facets, Advances in Cardioology. Karger 2008;45:107-113

3. Whitmer RA. Type 2 diabetes and risk of cognitive impairment and dementia. Curr Neurol Neurosci Rep 2007;7(5):373-380

4. Kulstad JJ, et al. Differential modulation of plasma beta-amyloid by insulin in patients with Alzheimer disease.
Neurology. 2006;66(10):1506-10.

20 Responses to Why big bellies could mean big trouble for brain function in later life

  1. Anna 28 March 2008 at 3:42 pm #

    Yes, wheat bellies. I’ve noticed my neighbor has developed a slight one in recent years. It isn’t from lack of exercise; he has a manual labor job and is gets a workout from his daily activities.

    BUT, in recent years, his wife has implemented “healthy lifestyle”. They have reduced red meat to almost nil; reduced saturated fat from their diet and increased vegetable oils; and they have shifted to more “whole grain” flour products. Sigh.

    He did a job for us and I cooked some local eggs in butter for him and I thought he was in heaven, after so many “Egg Beaters” and bran cereal bowls.

    Now his doctor is suggesting a statin because his cholesterol profile has shifted negatively, despite the “healthy lifestyle”. He was open to a low carb way to deal with this, but his wife completely shut down the notion. Sad.

  2. Dr John Briffa 28 March 2008 at 3:48 pm #

    She’s not trying to kill him off with a high-carb diet is she? (That’s a joke, by the way…)

  3. Liz 28 March 2008 at 4:02 pm #

    When I saw the “big belly” in the title I immediately thought of Homer Simpson!

    So it’s not just the beer that leads to the big belly and also causes dementia!

    And just a thought – if Homer ever got dementia, would anyone know the difference?

  4. Carmen 28 March 2008 at 6:08 pm #

    I have been Nursing ,Dementia’ patients for 28years now,
    I have looked after many people in their own homes, at
    present my patient has been suffering from ‘Dementia’ for
    the past nine years, her GP told us she was in her last stages about two years ago, she is still here and smiling and talking,
    I cannot see what having a ‘big belly’ has got to do with ‘dementia’ all the people I cared for were very slim.

  5. Sue 29 March 2008 at 12:04 am #

    The big belly usually means they are having a high sugar diet. Elderly people don’t usually have a belly – they may of when they were younger but as people age a lot of them lose weight and look frail – perhaps because they don’t seem to absorb the nutrients very well from foods they eat and they don’t eat very healthily, especially if they are in a nursing home and eating all that stodge and becoming protein deficient.

  6. Sue 29 March 2008 at 12:08 am #

    I think I read it on McCleary’s blog that in the brain you may get Type 3 diabetes – just like type 2 the brain becomes resistant to insulin causes all sorts of problems – dementia being one of them.

  7. Vital Wellness 29 March 2008 at 12:36 am #

    There are many factors involved here. I believe generally that people who do not take care of themselves(overweight) are also lacking exercise, proper nutrition, suffer from toxicity and potentially not dealing with stress properly. The weight issue is probably indicating the these factors.

  8. Tiggy 29 March 2008 at 12:53 am #

    Okay so how does one measure this belly thing? And what exactly is the midriff? Is this different to a waist measurement? I mean what exactly is meant by ‘the middle’? It’s not exactly a scientific term. I thought I was safer because I go in at the waist and my waist isn’t too big, but if the measurement is lower down…hmm…bad news. Perhaps this explains why I can’t do chemistry equations.

    Women with PCOS/Stein-Leventhal syndrome often have short term memory loss. Is that connected?

  9. Charlie 29 March 2008 at 10:05 am #

    She disses it totaly:

  10. Dr John Briffa 29 March 2008 at 10:25 am #

    That’s fair enough to find fault in the original study, but I recommend we do not lose sight of the fact that individuals with impaired glucose metabolism/diabetes have been shown to be at increased risk of cognitive decline, and there are known mechanisms that may explain these findings. And there is good reason, I believe, to be wary of the need to control blood sugar and insulin levels if we’re looking to reduce risk of mental decline/dementia.

  11. Steve T 29 March 2008 at 1:16 pm #

    I believe we’ll eventually find that increased intake of insulin-raising carbohydrates will be linked to many of the crippling “western” diseases we face regardless of whether the individual gets obese as a result. There are lots of thin people that have cholesterol problems. The fact that they don’t suffer from obesity seems to be unrelated to the onset of insulin-related problems later in life.

    This study might be a result of the “low-hanging fruit” syndrome. Finding people with an increased incidence of dementia amongst the obese is not surprising. If someone could do a detailed study of lifetime carbohydrate consumption and its relationship to the onset of disease later in life, I believe we would see an association between high-carb eating patterns and dementia regardless of whether one also becomes obese.

    In other words, the increasing incidence of dementia may not be related to obesity, but rather the per-capita increase in carbohydrate consumption in the western world in the last century or so. The fact that some fail to grow obese as a result of higher carbohydrate consumption doesn’t offer much protection from the other damaging effects of higher levels of insulin in the body chemistry, like heart disease, bad lipid profiles, etc. Plenty of slender folks suffer from those maladies as well.

    I believe we’ll eventually find that obesity and dementia will be linked back to excess insulin production. One doesn’t cause the other; they’re both caused by the same thing.

  12. Sue 30 March 2008 at 1:05 am #

    Steve, you’re absolutely right. Some may display obesity as a sign of excess insulin whereas others will remain slim.

  13. Megan 31 March 2008 at 9:00 am #

    All three close friends and relatives who developed dementia were slim and physically fit. It doesn’t seem to make much sense, does it?

  14. bob 31 March 2008 at 10:17 am #

    I bet if you looked at alot of these people they are eating tons of fat as well as carbs . It is far too simple to blame carbs – most of these people eat loads of crsps, fries, cake etc. plus excess alcohol!

    Everyone on here just seems to blame carbs – which is clear nonsense.

  15. Dr John Briffa 31 March 2008 at 2:30 pm #

    The ideas here suggest that the factors involved in causing abdominal obesity are A potential cause of dementia, not THE cause. Plus, I suspect nothing will make much sense if you use (limited) anecdotal experience to trump wider evidence in the research.
    What we have here is evidence linking abdominal obesity with increased risk of dementia and some plausible explanations for common underlying factors (i.e. carbohydrate and insulin excess).
    If you have any evidence that, you believe, disproves these ideas or proves some other mechanism then please provide it. Please do refer to published research if you can.

  16. bob 2 April 2008 at 8:34 am #

    dr Briffa – I guess you do not like comments on here unless they are science. I looked at your site for ideas about food and eating as you say you are a nutritionist but there is nothing on here at all apart from the usual carb bashing I see on other low carb nessage boards. No practical advice what so ever.

    Surely it is common sense to not eat excess fat – apart from the fact that food with alot of fat is not that nice. you know all the fried stuff.

    I am intriqued by your book someone lent it to me – who are you aiming it at – not people on a budget. The recipes are completely impractical and expensive – venison , t bones – I recently bought a t bone cost me £18 so for my family that recipe would cost me nearly £120 ! They allso seem to have ingredients that you said not to use like sugar and alcohol.

    Obviuosly you do not welcome people here unless they quote a study or agree with your ideas.

  17. Dr John Briffa 2 April 2008 at 10:06 am #

    Pretty much all views are ‘welcome’ here, but it does help if comments are well argued and/or science-based. Yours, in my view, are neither. So please don’t be too surprised or upset if you don’t get a completely free ride here.

  18. bob 2 April 2008 at 1:54 pm #

    you havent commented on the book .

    You say in your intro you cut thro the hype but there is no practical info on here at all – any comments.

    So basically you only want evidence is that what you are saying.

  19. Dr John Briffa 2 April 2008 at 2:42 pm #

    What has the practical advice I offer (by the way, there’s plenty of food and meal suggestions and recipes in the book) got to do with ‘cutting through the hype’? (answer: nothing).
    No, it’s not only evidence I want, necessarily. Something, well argued (as I said before) and intelligent would be a good start. As usual, you’ve failed to provide anything remotely cogent.
    If you want me to post your comments and take them seriously in the future, I think you’re going to need to step up your game a little (a lot, actually).

  20. Sue 6 April 2008 at 12:52 am #

    Bob wrote:
    “I bet if you looked at alot of these people they are eating tons of fat as well as carbs . It is far too simple to blame carbs – most of these people eat loads of crsps, fries, cake etc. plus excess alcohol!

    Everyone on here just seems to blame carbs – which is clear nonsense.”

    Fat and carbs in combination and eaten to excess is a recipe for weight gain. Most of the foods mentioned above would be full of unhealthy fats like trans-fats not the beneficial saturated fat. Carbs are targetted because they are a big problem for people who want to lose weight and are insulin resistant. When they go on a lower carb diet they lose weight. If you can eat more carbs and remain lean then good for you alot of people cannot.
    Another thing, just because someone is lean doesn’t mean they are healthy, they may be able to remain lean whilst eating a tonne of carbs but being lean doesn’t exclude you from getting a disease.
    Our bodies need fat and protein but do not require carbs.

Leave a Reply