Ben Greenfield on the 4 Dangers of a Low-Carb, High-Fat Diet

Ben Greenfield is author of the new book “Beyond Training”, in which you learn how to be healthy on the outside and inside, how to interpret your own biomarkers, and how to achieve amazing feats of physical performance without destroying your body or mind.Share5

Credit: Flickr Commons, Adam Wyles

I personally have experimented with very low carbohydrate diets combined with extreme amounts of exercise and have certainly noticed issues on my biomarkers of which I would have never been aware if I weren’t testing and tracking – and these were serious issues that threatened my long term hormonal health and longevity.

With low-carb, high-fat diets becoming more mainstream for everything from weight loss to physical performance, it’s very important for you to be aware of common pitfalls with this diet – particularly pitfalls that may be directly quantified in your own blood biomarkers. Here are four dangers of a low-carb, high-fat diet that you need to be aware of:

1. Triglycerides

Not only are high levels of circulating triglycerides a good way to get fat fast, but studies have consistently linked high triglyceride levels with heart disease, heart attacks and stroke. Fructose is one quick way to elevate triglycerides, but this really doesn’t seem to be an issue with high-fat, low-carbers. However, vegetable oils and animal fats can also raise triglycerides. The big issue here is that if these oils and fats have been exposed to high amounts of temperature and processing, triglycerides are getting dumped into your body chock full of free radicals. So if your high-fat diet includes a high amount of roasted seeds or roasted nuts, nut butters, heated oils such as heated coconut oil or heated extra virgin olive oil, barbecued meats or meats cooked at very high temperatures, then your triglyceride count is going to go up. You should have triglycerides that are less than 150mg/dL, and a triglyceride to HDL ratio that is no more than 4:1, but in most of the healthiest people I’ve worked with, triglycerides are under 100 and the triglyceride to HDL ratio is less than 2:1.

2. Inflammation

If you have high levels of cholesterol (which you probably do if you’re eating a high-fat, low-carb diet, then you need to be worried if your HS-CRP levels (a primary marker of inflammation) are above 1.0 mg/dL – even if you’re a hard charging athlete. I like to see most people under 0.5 for CRP levels, and here’s why: a high amount of inflammation in your body is going to make the cholesterol circulating in your bloodstream more likely to become oxidized, generating a high amount of heart and connective tissue-damaging free radicals. As a matter of fact, it’s more dangerous to have high levels of cholesterol and high levels of CRP than low levels of cholesterol and high levels of CRP – even if your high levels of cholesterol are “healthy”, big fluffy LDL particles, and not small, dense vLDL particles. In other words, no matter how many healthy fats you’re eating, these fats may actually come back to bite you if you’re creating high inflammation from too much exercise, not enough sleep, exposure to toxins and pollutants, or a high-stress lifestyle.

3. Glucose/HBA1C

Free-ranging glucose molecules in your bloodstream can adhere to cholesterol particles and cause those particles to remain in the bloodstream for long periods of time, since your liver can’t properly process cholesterol when it has a glucose molecule attached to it. The longer cholesterol circulates in your bloodstream, the higher the likelihood that it will dig its way into an endothelial wall and potentially contribute to atherosclerosis or plaque formation. This is why it’s so dangerous to eat a high-fat diet, but to also have your nightly dark chocolate bar, overdo it on the red wine, or have weekly “cheat days” with pizza, pasta, or sugar-laden ice cream. If you’re going to eat a high fat diet, then you need to ensure your fasted blood glucose levels are staying at around 70-90mg/dL, and your hemoglobin A1C (a 3 month “snapshot” of your glucose) is staying below 5.5. If not, your high fat diet could actually be significantly hurting you.

4. Thyroid-stimulating hormone (TSH)

Carbohydrates are necessary for the conversion of inactive thyroid hormone to active thyroid hormone, and if you’re on an extremely strict low carbohydrate diet, then you may actually be limiting this conversion. Your TSH is what tells your thyroid gland to “release more hormone,” so your TSH rises when your thyroid gland is underactive, or conversion of inactive to active thyroid hormone is inadequate. A high TSH means that the pituitary gland is releasing its hormone to try to get the thyroid to respond and produce more thyroid hormone. Because of inadequate carbohydrates, TSH will often elevate in a high-fat, low-carber – indicating potential for long-term thyroid and metabolic damage. If I see a TSH above 2.0 or a trend towards higher values in someone who is testing repeatedly, I get worried – andprefer to see TSH at 0.5-2.0. Of course, this doesn’t mean that you begin to shove carbohydrates indiscriminately down the hatch. However, it means that your high-fat, low-carb diet should include thyroid supporting foods rich in iodine and selenium, such as sea vegetables and brazil nuts, and should also include carbohydrates timed properly, such as before, during or after workouts, when the carbohydrate is more likely to be utilized for energy and less likely to spike blood glucose levels.

7 Replies

  • Hi ragivrao

    Did you read more the comments posted on the same article from Ben?

    Ok here's the article (your source of post) and comments that follow in the comments section:

    You will find me there also ... read this way back in Nov 2014, when I first commented on that article. 90% disagreed with his take and my comment has 26 likes :)

    Hyper-responders will have trouble with LIPIDS on High Fat and going too low on carbs. But, that number is very small. There's one LCHF diet diabetic user -- pdiabet -- on my forum who has really posted about his practical experience and how he decided 50 grams carbs is not for him so switched back to 100 and cut down on SFA a bit. We experiment and reach our own goals. We do read everything but we read SCIENCE and interpret and not believe blindly. We believe in what our medical reports say.

    There's no danger of LCHF for those who know how to work with it. For those who haven't/can't everything is bad about LCHF :)

    Any idea who sponsored his book?

  • Fact that you commented on his article in November 2014, shows that you read a lot. I just saw one guy getting on your tail, Josh Finlay some 20 odd year old kid. When people cannot debate they get personal and insult as usual -- he did the same in the end. Nothing surprising even there.

  • I've commented on this in another post:

  • Hi Concerned,

    On the article that I linked, there was one fanboy and 90%+ of others disagreed entirely with the article. The moment I read the title of this article, I knew this was the article.

    Surprisingly, I find that 85 comments back then (around April 2015) are now reduced to 33. Looks like Ben removed 50+ of the comments as almost everyone was in disagreement with his point of view :)

    I had posted my first comment was back in Nov 2014 on the same article and posting through FB makes my identity real.

  • Maybe I'm coming down with something, because I'm sick and tired of all this manipulation and vested interests, lol :-D

  • Why not write a book? ;)

  • Sorry but Ben Greenfields summary is as follows:


    As you can see from just the preliminary data and from Part 1 of this series, there is strong evidence that:

    -Eating a high fat diet doesn’t make you fat.

    -Eating a high fat diet can increase the amount of fat you burn as fuel at both rest and during exercise.

    -Eating a high fat diet can allow you to exercise or function for longer periods of time while eating relatively few calories.

    -Avoiding high carbohydrate intake improves health and doesn’t limit performance.

    -Someone needs to tell the folks a UConn to get bigger smoothie cups.

    From the muscle and fat biopsies to the urine and stool samples to the cheek tissue results, the data from the FASTER study at UConn will continue to pour in, and as it does, I will report back in the comments section below.

    Come here to see the whole story on how he uses fat for endurance athletics and achieves the unachievable by burning up to 3x more body fat than a sugar burner during similar exercise.

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