Yes, a low-carb diet greatly lowers your insulin


Less carbs, less insulin

Is “eat less and move more” really the only thing you need to know in order to lose weight?

Why is it then that most people lose weight on an LCHF diet, even when eating until satisfied and without even any increase in exercise?

The best explanation, in a simplified version, looks like this:

Carbohydrates – > insulin – > obesity

Thus more carbohydrates lead to more insulin which leads to more fat accumulation. With more details this can be written as follows:

Too many (bad) carbohydrates – > pathologically high insulin levels – > obesity

What constitutes “too many” varies from person to person depending on sensitivity and activity level (how much carbs you burn). Intensely exercising young men can often tolerate a fair amount of carbs, while heavily overweight older individuals with diabetes can only tolerate minimal amounts without problems.

The opposite is the following:

Less carbs – > lower insulin levels – > loss of excess fat

Insulin is a fat storing hormone. And the easiest way to increase your insulin levels is to eat more carbohydrates. The easiest way to lower insulin levels is to eat fewer carbohydrates.

This seems very straight forward. But some are still adamant opponents. Without being able to come up with any better explanation as to why a low-carbohydrate diet works (it does) they still don’t want to accept this explanation. They come up with all kinds of objections. Some don’t even want to recognize the most basic, that carbohydrates increase insulin levels or that a low-carb diet lowers insulin levels.

Their complicated objections don’t matter much in reality. The truth is clear in study after study on humans. Insulin levels are much higher when you eat a lot of carbohydrates and lower on a low-carb diet. The figure above (from Boden et al.) is one example.

Here are some more:

Much lower insulin levels on a low-carbohydrate diet


Figure from Noakes et al.


Figure from Hernandez et al.

Longer trials

The insulin-lowering effect of low-carb diets has also been demonstrated for fasting insulin levels, in longer RCTs like these: NEJM 2003, Lipids 2009.

Lower insulin, lower insulin, much lower insulin

Does a low-carbohydrate diet lower insulin? There is only one answer: Yes, insulin levels decrease greatly throughout the entire day.

One could only wish that the insulin deniers could at least accept something this basic.


The #1 cause of obesity: insulin

It’s the insulin, stupid!

LCHF for beginners

How to lose weight


Even fasting insulin levels have been shown to be lower on a low-carb diet (for example: Samaha et al., Volek et al.)

1 2


  1. robert
    It seems your pancreas' function is very limited, but still sufficient for very low carb food. There are tests to determine how much insulin the beta cells can still produce, which should give some more info if your specific problem. Lack of insulin production vs insulin resistance or even both. More data points for a better plan of attack.

    I have no personal experience with fasting (except during sickness), but I have watched a couple of video lectures by Dr. Jason Fung about this treatment option and how it has helped many of his diabetic patients. A lot of common sense involved!

    His blog:


    All the best!

  2. sarah
    Some protein foods raise insulin more than CHO so how much protein do you need to eat to maintain low levels of insulin? Surely it can not be to to reduce protein and CHO?
    Reply: #53
  3. Zepp
    All proteins (amino acids) rise insulin.. thats good!

    It altso rise glucagon proportionaly.. its a zero sum game!

    And that is when insulin does its jobb.. let it do its jobb!

    The thing to be afraid of is Hyperinsulinemia.. it is altso doing its jobb then.. but to coop whit a unnormal siuation!

    Its this unnormal situation/metabolic state that one should avoid.. often its about high glycemic load, insulin resistances, metabolic syndrome, diabetes!

  4. Susie
    My blood sugar levels are normal but my A1C is 5.9 - so I'm puzzled as to what is the best procedure for me. My weight is normal and I'm pretty active at age 71 - still clogging with the teenagers.
    Reply: #55
  5. Marty Kendall
    Based on the latest food insulin index data it appears that insulinogenic effects of dairy products, along with other foods, are largely explained by their carb, protein and fibre content. See analysis at
  6. Sarah
    I have a question! I have done nothing but try and fail at getting the extra weight off. I have done just about every possible diet plan. I have exercised to no avail. I recently decided to try to go low carb all day, then if I have any bread, rice or any kind of junk food I have it at night after my dinner. I have been steadily losing any where from 1-2 lbs a week this way. I found out a few days ago that they call this "carb back loading". Anyhoo, I decided to try this because I was tired of being sleepy and tired and having brain fog in the middle of my day. Now I see that low carbs equal no sleepy feeling or brain fog. My afternoon slump is considerably less. However I can't lie I have been having some junk at night. Now yesterday I made the mistake of making an exception and eating carbs in the middle of my day. It was munchkins from Dunkin Donuts to be specific. I took a nap shortly after eating this crap (surprise!) and shortly after I woke up I was shaking and feeling anxious. I checked my blood sugar and it was at 47! I am not diabetic or hypoglycemic so what was this about? Was it shock from eating what I normally don't eat in my day? The day before was Easter and I had a chocolate bunny and jelly beans my kids gave me for Easter, and had plenty of junk that afternoon at the family gathering with no problem. What made the hypoglycemia yesterday? (also I know you wonder why I check my blood sugar when I am not diabetic or hypoglycemic, and to make a long story short I had to prove to my drs that I am NOT diabetic! I have such anxiety at the drs that when they test my glucose at a physical it comes back at maybe 120. So to avoid having them try and put me through a 3 hr test I take my blood sugar BEFORE the appointment to show them that it was normal before I left my house that morning!)
    Replies: #58, #64
  7. Zepp
    First Im no doctor.. so dont take any advice frome me!

    But.. mayby you are not a diabetic.. or you are a prediabetic?

    One sign of prediabetics is reactive hypoglycemia.

    Anyhow.. let us see the truth.. your glucose metabolism is probably not healty?

    And the signs of that is that you are overweight (?), reacts positvely on a low carb diet, get brain fog by eating bad carbs, get hypoglycemic symptomes.

    Fasting blood sugar dont say that much.. A1c says more.. and a glucose loading test.

  8. Sarah
    Zepp, I have SUSPECTED insulin resistance. My doctors have told me this is not my case. My A1C was good. I have that exact result somewhere around here if I can dig it up I will post the actual number, but I do recall it was about 5.5. The A1C was done when I went for a physical and my fasting glucose was at 123 if I recall exactly. It was high due to my SEVERE panic I experience when I go to the Doctor. Flight or fight response is responsible for that. At Home my fasting blood glucose is never over 100. But I still suspect some kind of metabolic issue. I don't always believe Doctors are always right or that they even give us the whole truth. I think there are some who just wait for our health to go completely to crap because they either don't want to be bothered with helping a person get back to good health or they just want us to keep coming back to pad their wallet.
    Anyhoo, I am not USUALLY hypoglycemic. This was an isolated incident. I was wondering if that nap played a part in that? It was just weird. Of course if it ever becomes a regular thing I will be convinced that I have a medical reason for the reactive hypoglycemia. Also YES obviously all my weight loss efforts are due to having about 50 extra pounds on my body. I would surely not try losing this blubber if I didn't have it! LOL! I have been trying to do some research for answers or related info. After I commented here I was able to find where it was mentioned that sometimes the body can have reactive hypoglycemia if a person who is insulin resistant goes on a low carb plan. That really makes sense to me.
    Reply: #60
  9. Zepp
    Yes.. suspected pre-prediabetes then!

    It take at least 10-30 years to be a fully developed diabetic.

    Can be other things to but they are rare.

    In this 10-30 years FBG is normal or slightly elevated and altso A1c.

    Suddenly one get to that level that ones pancreas cant produce enough insulin to handle all glucos.. bang.. you got diabets typ2.

    And no.. its the oposite.. its less probably to get a reactive hypoglycemia whit low carb.. becuse you are not that dependant of glucose for fuel.

    Doctors do what they have learned and what symptomes they detect.. they cant see in to the future.. but there are better and worse doctors, as in all profesions.

    Heres an Yotube whit Dr Fung about the etiology of Diabets type 2.

  10. Sarah
    I am disappointed that Doctors so easily dismiss concerns. I think that more listening would benefit but what do I know! I am supposing since my numbers are not abnormal the think I have no reason to be concerned. Either way finding a dietary change that actually helps is encouraging to me. I was worried I was doomed to be fat forever no matter what I did. I Don't know that this is necessarily considered LOW carb being that when I do eat carbs I have them mostly at dinner. But going low carb at least during the day has been very helpful. People think I'm crazy when I say how different I feel. Thanks for the link!
  11. Sarah
    Maybe I'll update my weight loss in a month.
  12. Aly
    Any suggestions to lower insulin levels beyond carbs?

    Fasting in the 60s. Frequent hypoglycemia no matter the carbohydrate level (no, low, high) with in a few minutes after eating.
    (late /2+ hour hypoglycemia =insulin resistance; early/under 2 hours hypoglycemia =hyperinsulinemia with out resistance)
    Labs show high fasting insulin.

  13. alexchan
    i think this is the answer to your question.
  14. BLS
    Reply: #66
  15. Apicius
    Not sure I'm following your logic. When someone fasts, they deplete their glycogen storage (first the liver, then muscles). This then follows with the body being encouraged to switch to ketosis, the other fuel-burning regime. If some maintains a ketogenic, or low carb regimen when not fasting, the process to switching into fasting ketosis is easier. And, from a hunger point of view, a person who is in ketosis or low carb eating when not fasting will not feel as hungry when they start the fast. People who eat higher levels of carbs burn out their glucose inventory and feel hungry within a couple of hours or so (and thus the "snacking epidemic" was born).
  16. DrC
    How long does it take to see a decrease in A1C when starting a LCHF/IF diet? A1C in December 2016 was 5.9. Began LCHF/IF diet on January 2, 2017 and have lost 24 pounds in about 100 days. Repeat A1C this week remained at 5.9. Liver enzymes moving toward normal (I have NASH), but was hoping to see a reduction in A1C. Does this metric lag with dietary change? Thanks
  17. 3 comments removed
  18. Liam
    Hi, can anyone comment on a question I have, I have hypothyroidism for which I take NDT but I struggle with drowsiness at times, mainly when reading and while trying to focus and stay alert at church during sermons. Can this be a symptom of a metabolic disorder/blood sugar/too much insulin? I've just re started low carb after falling off the wagon about 6 months ago. Before that I was low carb for about 6 months. Many thanks
    Reply: #72
  19. Kristin Parker Team Diet Doctor

    Hi, can anyone comment on a question I have, I have hypothyroidism for which I take NDT but I struggle with drowsiness at times, mainly when reading and while trying to focus and stay alert at church during sermons. Can this be a symptom of a metabolic disorder/blood sugar/too much insulin? I've just re started low carb after falling off the wagon about 6 months ago. Before that I was low carb for about 6 months. Many thanks

    There are many many different potential causes of that level of fatigue, including thyroid medications. Please check in with your doctor who can do a more thorough analysis.

  20. Heather
    I have a question about lower carb fasting and reactive hypoglycemia. I don't have diabetes. I fast approximately 18-20/22 hours a day. I workout and continue my fast until I break my fast. I have been testing blood glucose. And for some reason and e I eat my glucose is down in the low 70's even if I eat a bit more carbs...any insight?
1 2

Leave a reply

Reply to comment #0 by

Older posts