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Low Carb, High Fat Doesn't Reduce Insulin Secretion

I posted a while back about my son’s type 1 diabetes diagnoses about 20 months ago. I personally have always favored a diet with 100-150 grams of carbs a day diet to lose fat and eating high fat. It certainly worked, but my son has now gone through periods with injected insulin where he ate 60%+ carbs with less than 30% fat and periods where he ate 20% carbs with high fat.

The shocking surprise was that he needed just as much insulin with 100 grams of carbs a day as with 300 grams of carbs a day, and much more insulin per gram of carbs on the high fat diet. So long as his calories were fairly constant, the reduction in carbs on a high fat diet is cancelled out by an increase in insulin required per gram of carbs. In other words he developed a kind of relative insulin resistance on a high fat diet that forced him to need much more insulin for the same amount of carbs, and the SAME amount of insulin overall to manage his diabetes through injected insulin.

SO a high fat, low carb diet does not seem to reduce the amount of insulin that he needs to inject, and by extension would not seem to reduce the amount of insulin secreted by a non-diabetic individual. This was a surprise to me. As a result I have been researching this phenomenon and found that muscle cells stop making glucose burning enzymes, and stop storing as much glycogen, while conversely making more fat burning enzymes and storing more fatty acids on a higher fat diet and that this makes the muscles poorer glucose burners and in effect it makes them relatively insulin resistant. There may be similar effect on the liver.

Studies have also found that individuals on higher fat diets will have higher fasting blood sugars and will also often fail glucose tolerance tests. It seems to be a short term phenomenon, but my basic question is, why do people turn to a low carb, high fat diet if it does not reduce the need for the body to produce insulin?

It DOES tend to lower peak blood sugars, and it does tend to prevent between meal hunger, but low carb, high fat does NOT seem to reduce the amount of insulin that the body need produce and secrete on a daily basis.

My son currently eats a variety of food and tends to get moderate carbs and higher fat, and the result is fairly stable blood sugar with relatively few low or very high blood sugars like a lot of kids, but it does not reduce his overall daily insulin needs at all.

For example, he typically eats about 30-40 grams of carbs at a meal with about 50% fat and about 500-600 calories. This would require about 3-4 units of insulin, but if he eats the same amount of calories with 100 grams of carbs, therefore 75-80% carbs (which we tested for 2-3 weeks) he still only needs 3-4 units of insulin for the 100 grams of carbs!

Anyway this has changed my view somewhat on how I feel about low carb diets as they clearly seem to make insulin less effective per gram of carbs almost in direct proportion to the reduction in carbs, ie no change in insulin needs.

For me it just works. My bloodwork is better, I have great energy, I stay leaner easier, and i’m stronger, without ever feeling deprived. I feel better running on fat and what you just wrote my be the physiological mechanism why, my muscle may run better fat adapted.

and as I think I’ve said before The insulin required to take in carbs really only matters if you are taking in carbs. If you don’t really eat carbs, insulin sensitivity is a fairly moot point. I also think it may be a little different in a non-diseased individual when accounting for training. If you only have some carbs after training insulin requirements may be low anyway.

It’s also interesting to note that this would put to rest one of the big anti-fat based diet claims. Mainly that you don’t stimulate enough insulin production.

I agree with this, except that insulin sensitivity is not really a moot point because your liver releases glucose throughout the day even if you don’t eat any carbs, so insulin resistance will still require more insulin to balance the release from the liver, but yes I agree with your points, I only wish to point out that low carb, high fat does NOT work (at least long term) via reduction in the body’s production and release of insulin.

I actually think part of the problem with high carbs is LOW blood sugars, ie crashes because of high insulin SENSITIVITY on a low fat diet, and also that a meal of carbs will pretty much be done providing energy within 2 hours while a high fat meal will provide energy for more hours without blood sugar coming down very low.

Also wanted to mention that my son is very lean but takes about 2-3 times the insulin per the same amount of carbs as kids who eat 55-70% carbs and end up over weight. One of the main reasons is that he doesn’t feel like eating 2 hours after a meal so I don’t end up having to give insulin constantly for 2-3 snacks in addition to meals. He also is less prone to low blood sugar with activity apparently because his muscles use fat up to a higher work threshold.

Regarding the liver issue, even if you only eat FAT your body will need to release insulin to keep the liver from over-releasing glucose and raising blood sugar too high, and the amount of insulin needed to keep the liver in-check will go up on a higher fat diet because the muscles will not have the same capacity to take in and use the circulating blood sugar, SO eating fat (even 100%) DOES stimulate a higher release of basal (round the clock) insulin.

Any info on what these differences do to the other anabolic/catabolic hormones? While insulin is important and powerful, it isn’t the only thing. What does it do to glucagon do and does a persons sensitivity to other hormones change?

Interesting discussion. Couple things:

  1. Regarding the scenario of your son needing the same units of insulin for 30-40g of carbs and 100g of carbs. Are these the same type of carbohydrates and fats in each meal, just ratio’d differently? I.e. low or high glycemic, saturated, unsaturated, etc.

  2. Another point about the importance of insulin sensitivity, at least in regards to muscle, is the increased uptake of amino acids and the effect that has on protein synthesis.

  3. Considering the inhibitory effect insulin has on lipolysis, it is interesting to think about what that means in regards to high fat/ low carb diets stimulating higher amounts of basal insulin secretion.

  4. Chronic insulin resistance is a pretty good indicator for metabolic syndrome which brings along with it a whole host of other hormonal problems like lower GH, higher cortisol, obesity which can lead to excess aromatization and a higher E/T ratio.

  1. Yes same components, though I should add that if he eats low fat for multiple days in succession he needs even LESS insulin. In other words, the first day he might need more insulin for the 100g carbs/low fat than the 30-40 gs with high fat but by the third day of reduced fat the ratios have changed completely. This is consistent with the fact that people will often fail glucose tolerance tests if they eat low carbs, but that 3 days of higher carbs will tend to move them back to a passing GT test. There was an experiment done with two men who ate virtually zero carbs for a year (almost 100% meat) in which they totally failed glucose tolerance tests (peak glucose levels of 250-265!) but after a week of eating carbs they had pretty normal GT tests.

  2. Protein clearly requires injected insulin. In fact I have considred that this might be a reason why some trainers have gotten good results on 300+ grams of protein when there is simply no way for all of that protein to be incorporated into muscles. The answer is that protein acts as a slow and steady insulin stimulator as a significant percentage of consumed protein is turned into glucose but in a slow steady fashion.

  3. If I remember correctly from discussions I have had with research endocrinologists, fat burning enzymes like hormone sensitive lipase get turned on when insulin levels drop, but it takes TIME for the enzymes to get turned on, its not just like turning on a switch. Reduced insulin also will always trigger protein degradation into glucose BEFORE it turns on hormone sensitive fat burning enzymes. This seems to be a big puzzle of body comp that low insulin always turns on gluconeogenesis from protein before it turns on fat mobilization.


Again it might suggest that low carb.high fat works for body comp primarily by stabilizing energy levels and preventing hunger, but low carbs also turn off leptin in 2-3 days which slows down metabolism.

  1. There seems to be a distinct difference between high fat consumption caused “physiological” insulin resistance and insulin resistance caused by chronically elevated insulin levels. I think it is important to realize that whether you eat low carb or high carb you will have chronically high insulin levels IF you eat a lot more than you burn all the time.

Lastly, something different may occur when carbs/protein get low enough to turn on nutritional ketosis. That certainly occurs because of low insulin levels, however the body will release insulin to try to shut off ketosis, and someone who is in nutritional ketosis who then “LOADS” on carbs will often have VERY high blood sugar when the carbs are reintroduced. Muscles stop producing glucose burning enzymes, and nutritional ketosis actually seems to cause insulin resistance (physiological) as muscles get fat loaded.

(Type 1 diabetics who intentionally eat carbs/protein at ketogenic levels require vary large amounts of insulin per a given amount of carbs).

Wanted to add something else. My son needs significant insulin just to manage protein, and yes insulin does move aas into cells, but as a result, in someone with type 1 diabetes it can raise blood sugar because it is using up insulin that would otherwise hold the liver in balance or be used to move glucose into muscles or the liver.

The effect of protein on blood sugar seems to actually be MORE significant if the protein is eaten with fewer carbs than with more carbs. Protein of course CAN move into cells without insulin but it will use insulin if it is available. Some of it will also get processed into glycogen in the liver and slowly released and again it takes insulin to balance this.

I tried the low carb thing but I lacked energy. Soon I drifted towards eating more greens. Now I don’t eat meat (Super rare) but I have a nice green smoothie like 2-3 times a day. Try that sometime. Proven to help people dramatically (Especially the diabetic).