Insulin Sensitivity Determines Effectiveness of Dietary Macronutrient Composition

[tortoise]

I just blogged on this new study. The essense is that level of insulin sensitivity determined what kind of diet worked best. (Low-carb is best for insulin resistance - no big surprise to us - but it was a nice comparitive study such as you rarely see.) The abstract of the study is at:

http://www.obesityresearch.org/cgi/content/abstract/13/4/703

My blog entry is at:

http://turtleway.modblog.com/core.mod?show=blogview&blog_id=623453

And copied here:

'm the kind of person who actually gets excited over good research. This study, from this month's Obesity Research, called Insulin Sensitivity Determines the Effectiveness of Dietary Macronutrient Composition on Weight Loss in Obese Women, is one of the good ones.

This is kind of weight loss study is so rare. Granted, it’s small, and it’s short-term, but basically that’s all the bad news. The good news is that it is a) extremely well-controlled, and b) it actually explores the effects of different diets on different groups of people based on a well-founded theory! As someone who tracks the obesity and weight loss literature fairly well, I cannot tell you how very unusual this is. As I learned in grad school statistics, when there are wildly varied responses to something (like diet), that’s when you start looking for subgroups. And that’s exactly what this study does.

The researchers hypothesized that people who are insulin resistant might respond better to a diet that was less glycemic (due to fewer carbs and more fat) than people who have normal insulin sensitivity. There are very solid reasons for thinking this might be the case. So they took a group of mildly-moderately obese women and put the ones who were most insulin resistant in one group, and the ones who were most insulin sensitive (least resistant) in another. They didn’t use people who were in the middle, to make the results clearer.

Next, they figured out everyone’s metabolic rate, body composition, and how many calories their bodies were using (believe me, you will not see this attention to detail very often!). Then, for 16 weeks, each subject was given food to eat that would be 400 calories less than they needed to maintain their body weight. Half of each group received a diet that was low in fat and high in carbohydrates, and the other half ate a diet that was low in carbs and high in fat.

The results were nothing short of astonishing. Despite being on diets where the calorie levels were tailor-made for each individual, the results varied wildly depending both upon diet content AND insulin sensitivity level:

- The insulin resistant people lost 13.4% of their body weight – average almost 25 lbs - on a low-carb diet, but only 8.5% (average 16 lbs) on a high carb/low fat diet
- The results for the insulin sensitive folks were precisely the reverse – 13.5% body weight lost (average 25 lb) on the high carb diet and 6.8% (average 13.5 lbs) on the low-carb diet.

Remember: they were all getting a calorie level custom-adjusted to each person!! And they were all getting their food from the clinic!

Other results:

- Fasting insulin levels dropped in all groups, but more in both insulin resistant groups.
- Insulin sensitivity improved in the insulin-resistant groups, the low-carb more than the high-carb (could be because more weight was lost).
- Triglycerides improved in all groups except for the insulin resistant group on the high carb diet. That group increased their triglycerides significantly.
- The two “mismatched groups” (losing the least amount of weight) lost the amount of weight that would be expected, given their calorie levels. The big mystery still to be solved is why the “matched” groups lost so much more that would have been expected.
- People did not report changing their activity levels through the study (and had been instructed not to).

Now, the study was awfully small (only 21 subjects), but given the size you’d actually expect less dramatic results. Also, it is short-term. We are all familiar by now with the track record for short-term vs long-term weight loss. Still, it was a carefully done study, and hopefully will be the foundation for many more along these lines. Congratulations to the researchers - well done!

[AntiM]

- The insulin resistant people lost 13.4% of their body weight – average almost 25 lbs - on a low-carb diet, but only 8.5% (average 16 lbs) on a high carb/low fat diet
- The results for the insulin sensitive folks were precisely the reverse – 13.5% body weight lost (average 25 lb) on the high carb diet and 6.8% (average 13.5 lbs) on the low-carb diet.
Thanks for the posting the research and your writing. Excellent!

It got me thinking ...

I spend most of my time in the TDC subforum. Many posters write about stalling after losing a big chunk of weight - despite taking measures like lowering calories or upping activity. We know that insulin resistance is helped with both LC diets and weight loss - so maybe some sort of critical mass is reached where LC is simply incapable of providing the same type of result.

If you're insulin resistent due you ever become truly insulin sensitive? And if you can develop that sensitivity, could LF be the best option for losing weight?

Any thoughts on this hypothesis?

[LadyArya]

Can someone clarify for me what is meant by insulin resistant and insulin sensitive?

[mcsblues]

Laura thanks for posting this ... but allow me to be picky for a minute!;)

40% Carbs is hardly a low carb diet - lower certainly, but it would have been nice to see them test their theory to its logical conclusion. The other point is that fasting insulin is not a particularly good measure of insulin resistance - something like the insulin challenge test the Eades describe would be much more informative. (Similarly a GTT is much prefered to a fasting blood glucose reading).

Lady Ayra - one of the pillars of any low carb diet is that with age and excessive carb consumption most of us start to require more and more insulin to enable the body to react to and deal with excessive blood glucose - which is what carbs become as soon as they are digested. We need more insulin, because the insulin receptors become less sensitive (or insulin resistant) over time (and carb overload) so more and more insulin is required to persuade them to do their job. The more insulin resistant you are the greater the problem and the closer you are to becoming a type 2 diabetic - where high insulin levels still cannot keep blood glucose in a normal range. OTOH the more insulin sensitive you are, the better - as you require only a minimal amount of insulin to accomplish the same task - so both serum insulin and glucose are kept in check - which means you are also much less inclined to store excess energy as fat, as the balance between the 'fat storing' insulin and its 'fat burning' counter hormone glucagon is maintained.

Monika, some people do regain some degree of insulin sensitivity through a low carb diet, exercise and weight loss - but you are unlikely to get back to eating like a teenager (sorry about that! :)) Either way, I certainly would not suggest you (or anyone) should ever go back to a high carb low fat diet - for most of us, that is how we developed the problem in the first place!

Cheers,

Malcolm

[Lessara]

- Insulin sensitivity improved in the insulin-resistant groups, the low-carb more than the high-carb (could be because more weight was lost).


Excuse me? I Didn't lose for 2 months! and my sugar still went from 160 monthly to 130 monthsly!!! Low carbing is great for me in this regard!! Only for because of losing weight, right! - Not!!

[tortoise]

40% Carbs is hardly a low carb diet - lower certainly, but it would have been nice to see them test their theory to its logical conclusion. The other point is that fasting insulin is not a particularly good measure of insulin resistance - something like the insulin challenge test the Eades describe would be much more informative. (Similarly a GTT is much prefered to a fasting blood glucose reading).



Totally agree, Malcolm - what impressed me was that a) for a study of its kind it was very well-controlled (there's always something else that can be done) and b) it got such dramatic results in spite of these limitations.

Do you think it would have been more accurate to say there were measuring insulinemia, rather than insulin resistance?

[tortoise]

Excuse me? I Didn't lose for 2 months! and my sugar still went from 160 monthly to 130 monthsly!!! Low carbing is great for me in this regard!! Only for because of losing weight, right! - Not!!

I've actually regained some weight all my bloodwork is still great, including blood glucose, which was borderline before. The researchers were observing a correlation that the more weight lost, the better the improvement in insulin sensitivity. That doesn't necessarily mean that there is a cause-effect relationship, but that was the conjecture of the researchers.

[IdahoSpud]

It's hardly surprising that the low(er) carbohydrate diet worked best on those who were most insulin-resistant.

The surprise (for me, at least) is that the low-fat, high carb diet worked so well in the least insulin-resistant group.

Correct me if I'm wrong: Are the results saying that a low fat diet actually works *better than LC* for people who are overweight but only mildly insulin resistant?

[tortoise]

The surprise (for me, at least) is that the low-fat, high carb diet worked so well in the least insulin-resistant group.

Correct me if I'm wrong: Are the results saying that a low fat diet actually works *better than LC* for people who are overweight but only mildly insulin resistant?

Well, as far as I can tell, they wouldn't be classified as insulin resistant at all (although as Malcolm points out, they were actually measuring insulin levels, not resistance, which is not a perfect way to measure). I've got to admit that I assume that most overweight - or at least obese - folks are insulin resistant. So it was a surprise to me that apparently a quarter of the people they originally tested would be classified as in the normal range, insulin-wise.

[Zuleikaa]

I'm not surprised. People become overweight for varying reasons. And while, I believe, most obese people have insulin issues some definitely don't.

It takes all kinds.

[VALEWIS]

I suppose we might consider that (surprise) there are complex variations in factors that result in overweight...so many become fat because they develop insulin resistance due to hi carb, and others become fat because they eat too many calories and don't exercise enough, and others because their hormones are out of whack, others because of aging factors and so on. So perhaps just lowering calories was enough for the folks that measured at normal insulin levels.

What I want to know is why do some people become insulin resistant to carb consumption and some don't? Genetic? Think of your skinny friends who eat heaps of carbs and sugar.

I think that it will be a wonderful day when the emphasis is on health rather than appearance...the skinny folks eating lots of carbs are likely to develop some nasty diseases.

Val

[ItsTheWooo]

It's hardly surprising that the low(er) carbohydrate diet worked best on those who were most insulin-resistant.

The surprise (for me, at least) is that the low-fat, high carb diet worked so well in the least insulin-resistant group.

Correct me if I'm wrong: Are the results saying that a low fat diet actually works *better than LC* for people who are overweight but only mildly insulin resistant?

Well I know when my sister tried Atkins she found no benefits. She was hungrier and ate more and did not lose weight.

I guess it could be true.

[AJCole]

I take from this that if you are insulin resistant, you need lc. But if you are not insulin resistant, calories matter. Perhaps it was not that the diet was low fat, but low calorie.

I know that at my heaviest, low carb was great, but I did not have to watch my portions to lose weight. Now, I have little to lose, I believe I am no longer insuline resistant (based on my own study of post carg-binge ketone strip analysis), but I have to keep my portions (and therefor calories) small to have a positive ketone strip.

Maybe this study demostrates the same thing. The one thing they do not tell us is how many of the insuline resistant women were more obese compared to the non-insuline resistant women. It would make sense if the non insuline resistant had the least to lose anyway.

[ddaniels]

Thanks for the posting the research and your writing. Excellent!

It got me thinking ...

I spend most of my time in the TDC subforum. Many posters write about stalling after losing a big chunk of weight - despite taking measures like lowering calories or upping activity. We know that insulin resistance is helped with both LC diets and weight loss - so maybe some sort of critical mass is reached where LC is simply incapable of providing the same type of result.

If you're insulin resistent due you ever become truly insulin sensitive? And if you can develop that sensitivity, could LF be the best option for losing weight?

Any thoughts on this hypothesis?

I've wondered about this too. I know I was insulin resistant, based on my high fasting insulin levels. My fasting blood sugar and fasting insulin levels are now in the normal range and since that time my weight loss has slowed a lot. Although I am "only" 13 lbs/ from my goal, in reality it's a pretty high goal- it's the highest I could weigh and make it into the "normal" BMI range. I'd prefer to be in the middle of the normal BMI range, which I think is probably a better match for my frame, whcih really means I could stand to loose about 23 lbs. So, I'm not sure if my weight loss has slowed just because I'm getting closer to goal. I've wondered if my metabolism has now shifted in some way to favor the more tradtional low-fat approach. (I sure hope not!)

[AntiM]

Perhaps it was not that the diet was low fat, but low calorie.Then, for 16 weeks, each subject was given food to eat that would be 400 calories less than they needed to maintain their body weight.

{snip}

The results for the insulin sensitive folks were precisely the reverse – 13.5% body weight lost (average 25 lb) on the high carb diet and 6.8% (average 13.5 lbs) on the low-carb diet.I think that indicates that diet composition was very important in rate of weight loss, not just calories.

I've wondered if my metabolism has now shifted in some way to favor the more tradtional low-fat approach. (I sure hope not!) Me Too! I love the food options of a LC WOE. I'd rather take longer to get to goal than eat food I dislike.

[mcsblues]

I've wondered about this too. I know I was insulin resistant, based on my high fasting insulin levels. My fasting blood sugar and fasting insulin levels are now in the normal range and since that time my weight loss has slowed a lot. Although I am "only" 13 lbs/ from my goal, in reality it's a pretty high goal- it's the highest I could weigh and make it into the "normal" BMI range. I'd prefer to be in the middle of the normal BMI range, which I think is probably a better match for my frame, whcih really means I could stand to loose about 23 lbs. So, I'm not sure if my weight loss has slowed just because I'm getting closer to goal. I've wondered if my metabolism has now shifted in some way to favor the more tradtional low-fat approach. (I sure hope not!)

Like I said before, fasting insulin (and fasting BS) are not good indicators of insulin resistance - particularly so if you are already eating low carb. LC works because the demand for insulin is much reduced in the first place and blood sugar is much more stable for the same reason. Now weight loss, exercise and long term adherence to a low carb diet may help you restore some degree of insulin sensitivity (or not) - and this is why all low carb authors suggest that in order to maintain weight loss we each need to find our own level of carb intake to match whatever our level of insulin sensitivity will allow. But for most of us this is still going to be 100g or less - which is a whole lot less than the high carb low fat brigade would suggest we all should adopt (regardless of insulin sensitivity and the blood sugar rollercoaster that will ensue if you go over your natural limit) That is not to say you couldn't maintain, or even lose weight on a low fat high carb diet ... if you kept calories low enough - I did it for 2 years before I discovered low carb - but I was constantly hungry, I was not healthy, and knowing what I know now, I am pretty sure I lost a whole lot of muscle as well as fat (due to insufficient protein). Regardless of weight loss, the health considerations alone make it pretty easy for me to decide which approach to continue to adopt.

If you are really interested in an accurate assessment of your current degree of insulin sensitivity, you could do a glucose tolerence test with regular insulin readings taken along with the blood sugar data, or preferably you could get your doctor to perform an insulin challenge test as described by the Eades in PPLP.

Cheers,

Malcolm

[ddaniels]

Like I said before, fasting insulin (and fasting BS) are not good indicators of insulin resistance - particularly so if you are already eating low carb.

Oops, I missed that! I guess I just naively assumed I was all "fiixed" since my lab work was normal. When I first had my fasting insulin tested I was already doing low carb and eating about 20 carbs/day. I had been doing it for about 3 months and had lost about 20 lbs. My fasting insulin was high (29 -Normal is <17) I continued to eat 20-30carbs/day and had it redone after about 8 weeks when I had lost another 15 lbs. At that time my fasting insulin was down to 11. I assumed something was getting better, since I had high insulin levels after eating very low carb for 3 months, and now those levels are down after continuing to eat the same way for 8 weeks more. But, as you say, the improvement may only be apparent because I am eating low carb, and that doesn't mean I can process 100 plus carbs/day as if there was nothing wrong. (Although 100 carbs/day seems like FEAST of carbs after what I've gotten used to, so I suspect I'll never get up to that number either!)

[joanee]

I'm a little lost. Assuming you are IR, and you cut carbs and cut fat, what is your body using for fuel? Aren't you then just eating your own muscle tissue for fuel? Also, assuming that through weightloss and regular exercise you regained some or all of your insulin sensitivity, wouldn't a return to a high carb diet just send you back into insulin resistence? What would be different the 'second' time around about eating high carbs? I have to say, I'd dread having to go back to a low-fat woe. This woe feels like the way my body has wanted to eat all along; I will also say, though, that something about the amount of saturated animal fats I eat makes me very uncomfortable. I can't put my finger on it, but it definitely bothers me. I tend to trim my beef and pork very lean because of it. Dark poultry doesn't make me uncomfortable at all.

[mcsblues]

I'm a little lost. Assuming you are IR, and you cut carbs and cut fat, what is your body using for fuel? Aren't you then just eating your own muscle tissue for fuel? Also, assuming that through weightloss and regular exercise you regained some or all of your insulin sensitivity, wouldn't a return to a high carb diet just send you back into insulin resistence? What would be different the 'second' time around about eating high carbs? I have to say, I'd dread having to go back to a low-fat woe. This woe feels like the way my body has wanted to eat all along; I will also say, though, that something about the amount of saturated animal fats I eat makes me very uncomfortable. I can't put my finger on it, but it definitely bothers me. I tend to trim my beef and pork very lean because of it. Dark poultry doesn't make me uncomfortable at all.
I don't think anyone is suggesting you go low carb low fat. Questions were rasised about going on to a low fat high carb low calorie diet to stimulate losing the final few pounds to goal - on the assumption that low carb 'cures' insulin resistance - which it doesn't (it may improve IR to a degree as time on a lc diet, weight loss and increased exercise take effect). I would be the last person to recommend you take this course of action (even though you might well lose weight if you kept calories low enough) because, as you say, your IR is likely to worsen and the other heath benefits of a healthy LC WOL will also slip away.

You are likely to be uncomfortable about saturated fat because we are relentlessly 'told' it is not good for us. But saturated fat from good sources is very good for you if you keep your carb intake down. Incidentally the fat you are trimming from beef and pork is less than 50 % saturated (there is a large amount monounsaturated with some polyunsaturated as well) If you can get it, grass fed beef or pork fat is much healthier than grain fed sources (like most poultry) - because of the lower percentage of omega 6 polyunsaturated fats, which we get too much of generally.

Cheers,

Malcolm

[K Walt]

"though, that something about the amount of saturated animal fats I eat makes me very uncomfortable."

The fat that your body makes -- even from 'wonderful' fat-free whole grains -- is about 44% saturated. If saturated fat were so deadly, why would the body CHOOSE to store its reserve fuel as saturated fat? Actually, because saturated fat is an excellent, clean-burning fuel -- fully field-tested in actual biological organisms now for 150,000 years. Good stuff.

[ceberezin]

The main problem with the conclusions of the researchers is that didn;t account for the fact that insulin resistance is cumulative. So those subjects who seemed to do well on the high carb-low fat diet are going to stop doing well on that diet if they keep it up. The fact that their fasting insulin was low doesn't mean that they weren't hyperinsulinemic under other conditions.

I would also like to know how they were defining insulin resistance and what were the ages of the people in the different groups. It is not accurate to say that people are either insulin resistant or not insulin resistant, as this study suggests. The question is what degree of insulin resistance do people have.

The following comment by the researchers is very telling:
- Insulin sensitivity improved in the insulin-resistant groups, the low-carb more than the high-carb (could be because more weight was lost).
They refused to believe the obvious, that insulin sensitivity is improved by carboydrate control, not weight control. Their eagerness to deny the results of their own study makes their conclusions suspect.

I am continually disturbed by the singular focus on weight loss. There are so many reasons to control insulin resistance besides weight loss. It is the key to health in general.

[bluesmoke]

People who can't grasp that eating a diet high in foods that lead to rapid rises in insulin release might be some bad for those who are insulin resistant are beyond the reach of logic. Nyah Levi