Insulin Resistance CAUSES weight loss? May 12, 2009
Posted by Dr Dan in Uncategorized.trackback
I recently read this study by Weddick et al. from the American Journal of Epidemiology (Vol 153, no 12: 1199-1205) that I found very interesting. I will attempt to plagiarise sum it up here.
Overall the study investigates the paradox that on the one hand insulin resistance increases with old age, and on the other weight loss also tends to increase. The authors investigated the association between these two parameters among 725 nondiabetic men and women aged betweem 50-89 yrs old. Weight and insulin were measured at baseline (1984-1987) and evaluated again later (1992-1996). Insulin resistance was defined as the top quartile of fasting insulin levels and this quartile was found to be significantly associated with weight loss!!! Results remained the same for men vs women, overweight vs normal weight, and for young (< 70 yrs) vs old (> 70 yrs). Insulin-resistant individuals had a threefold increase likelihood of losing 10 or more kg compared to those without insulin resistance.
But why? We have always been told that insulin resistances causes weight gain not weight loss!!!! Yet other studies exist which show that insulin resistance is associated with weight loss. Folsom et al. found evidence for high fasting insulin levels and low rates of weight gain in older adults (mean age 54 years) but not among young adults (mean age 25 years). Similar results have been found for Black women but not Black men. In Pima Indian children insulin resistance was found to predict weight gain but the opposite was found in young Pima adults. In Mexican Americans and non-Hispanic Whites higher fasting insulin levels were associated with a lower chance of weight gain. Thus, it seems that ethnicity could be important in the relationship between insulin resistance and weight gain. Several ideas have been put forward to explain this dilemma. The ‘thrifty genotype’ hypothesis suggests that those ethnicities genetically predisposed to diabetes also have higher levels of circulating insulin to promote fat storage during times of famine. This may work for the Pima children but falls apart with the adults and the other studies that showed that higher insulin levels were associated with lower rates of weight gain.
It has also been hypothesised that increased insulin resistance is a part of the ageing process, yet in this study the opposite pattern was observed. However, herein lies the secret. The oldest individuals were the LEAST insulin resistant and this was statistically significant! Therefore insulin resistance predicts mortality. i.e the least insulin resistant one is the longer they are likely to live independent of weight loss or gain. Yet weight does seem to have an influence. Increased insulin resistance with aging could be caused by an increase in visceral adiposity. Cefalu et al. showed that intraabdominal fat accounted for 51 % of the variance in insulin sensitivity. The authors in this study also found that insulin reistance was associated with less fat based on the waist:hip ratio.
I will discuss further explanations in the next few days.
In the study, did they look at initial body composition? Could the weight loss be a product of muscle atrophy?
I’ll admit I’m a bit mystified, Dr Dan. I look forward to your, and the study author, theories.
-Steve
Another thing to consider is a loss of muscle mass. That tends to happen in older people, especially the ones who are out of shape and likely to be insulin resistant.
Dan:
Grr… you spelled ‘Wedick’ wrong… The content of that article is free access:
http://aje.oxfordjournals.org/cgi/content/full/153/12/1199
As Stephan points out, weight loss is not necessarily fat loss. It’s more likely lean body mass loss (muscle, bone, and organ), which is essentially the slow process that eventually results in a death from natural causes as the digestive system fails. It was _only_ the heaviest group that lost weight as they aged, the others didn’t. Another pub from the same study:
http://www.ncbi.nlm.nih.gov/pubmed/12410899
Found that the more insulin resistant people who lost > 10 kg body did die at a significantly higher rate than the others. I think based on that, we can safely conclude they were not shedding body fat but rather vital organ mass. See Figure 1:
http://www3.interscience.wiley.com/cgi-bin/fulltext/118936542/main.html,ftx_abs
Subcutaneous fat is benign, visceral fat is not. This is yet another study that supports that notion. Interestingly, the two lighter quartile patient groups smoked and drank more than the most insulin resistant one.
I think the whole issue of insulin resistance is fascinating and poorly understood. Just fasting causes an increase in insulin resistance! That can’t be a pathological condition. I would guess that active fat loss (i.e.mobilization of free fatty acids from fat stores) due to caloric restriction, low carb diet or exercise is also associated with some amount of insulin resistance. To me this just means that the body has mechanisms in place to preserve blood glucose concentrations when it senses deprivation or catabolic conditions. So by this reasoning, you should expect some amount of insulin resistance to be associated with fat loss, but not necessarily causing fat loss. Of course it’s possible that there is some causative effect, as yet unidentified.
see this recent paper:
http://www.ncbi.nlm.nih.gov/pubmed/18986321?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.Pubmed_Discovery_RA&linkpos=4&log$=relatedreviews&logdbfrom=pubmed
There are lots more papers on pubmed, but little coherency as far as I can see. The more I read, the more I believe we have little to no understanding of what is really going on. The paradigm of “dietary fat leading to intramuscular fat stores and decreased insulin sensitivity thus leading to diabetes” is just so simplistic, and ignores the overfeeding of carbohydrates that has resulted in high triglyceride levels. But the earlier reasearch has been done with this bias that diabetes must be caused by dietary fat, and thus much of it just seems useless. The different types of fat (chain length, mono-, polyunsaturated vs saturated, etc) are clearly important, but we are only just beginning to sort out the details that affect health.
And now it’s back again… WordPress is acting up I guess.
Hmm… what happened to my comment?
I’d really like to hear more about this. I was diagnoses as pre-diabetic (insulin resistant) about two years ago. At the same time I found out I had an underactive thyroid. Both have been under control with exercise but I still have trouble maintaining a healthy weight. If I stop eating healthy or exercising I put the weight right back on, EVEN when my thyroid levels are normal.
If I was to guess, I’d say it probably has something to do with our body realizing something is wrong and trying to fix it. But who knows? Hopefully we will soon!
Rayna – have you been checked for food intolerances (gluten, casein,etc?) or tried anelimination diet to see if food intolerances are part of the problem?
The way our bodies react to changes and in healing is truly amazing.
Still don’t have any particular literature references, but insulin resistance could shift the homeostasis between weight gain and loss: if fat is stored and not released in the presence of insulin, but the tissues then become resistant to the action of insulin, it would be as if the insulin wasn’t even there. It makes sense. What I’ve heard is that sometimes muscles become insulin resistant before fat tissue, so fat is busily storing excess carbs and fatty acids as triglycerides while muscle isn’t removing sugar from the blood as it should, hence rising BG. When the fat cells become insulin resistant, maybe it could aid in weight loss, though no lowering of glucose. The body isn’t really stupid- it knows when it is overfed and needs to shed calories somehow.
Anyway, I’m sure there is an interesting story there, but no time to research it. Have you found out anything further?
Helloooo? Dr. Dan??? Your fans are missing you…please come back to the blogosphere!
What Stargazey said!!!! Come back Dr Dan!
Come back Dan – we miss you!
Hey, you should post more about this.nice post. Its a really well written article.
Steven T.
http://www.weightcontrolforever.com
i know insulin-resistance and weight gain go hand and hand according to the literature, but does anyone else find it counter-intuitive that the bodies decreased ability to carry sugar to cells (and eventually store as fat) wouldn’t result in weight LOSS?
Please write some more information on this stuff, the whole concept looks very interesting to me