# David Ludwig, Walter Willett, Jeff Volek and Marian Neuhouser: Controversies and Consensus on Fat vs. Carbs

David Ludwig is not a fan of lowfat diets. He is the author of Always Hungry, which includes this in its Amazon summary:

Low-fat diets work against you, by triggering fat cells to hoard more calories for themselves, leaving too few for the rest of the body. This "hungry fat" sets off a dangerous chain reaction that leaves you feeling ravenous as your metabolism slows down. Cutting calories only makes the situation worse-creating a battle between mind and metabolism that we're destined to lose.

But to write the November 16, 2018 Science article “Dietary fat: From foe to friend?” he teamed up nutrition researchers with different views. Together, they tried to identify areas of disagreement and areas of agreement. Let me briefly discuss the seven areas of agreement they found.

1. Both lowcarb and lowfat diets can work well. As I write in “Why a Low-Insulin-Index Diet Isn't Exactly a 'Lowcarb' Diet,” different kinds of carbohydrates differ dramatically in whether or not they cause insulin spikes. Lettuce, spinach, kale, broccoli, cauliflower and brussel sprouts technically have a lot of carbohydrates in them, but they are free of the easily-digestible carbs that turn into blood sugar quickly, which in turn causes a spike in insulin. A highcarb diet with little or no sugar and little or no processed food is a very different thing from what many people think of as a highcarb diet.

2. Saturated fats are bad. I think the jury is still out on this. Saturated fats are especially common in foods from animal sources, and foods from animal sources could have a lot of other problems. For example, I have been sympathetic to the idea that animal protein is a cancer risk. (See “Meat Is Amazingly Nutritious—But Is It Amazingly Nutritious for Cancer Cells, Too?”) And the most common type of milk in the supermarket has what appears to be a particularly dangerous protein in it. (See “Exorcising the Devil in the Milk.”) A good way to test how bad saturated fats are without results confounded by other problems in animal foods would be to have everyone in a clinical trial eat a vegan diet (as similar in other ways as possible), with half of them eating a diet with a lot of coconut milk in it, the other half avoiding all plant foods that have a lot of saturated fat.

3. Avoid sugar, refined grains and potatoes. Yes!

4. Lowcarb, high fat diets may be good for people with insulin resistance. Yes. And a large share of all Americans have insulin resistance to some degree.

5. Ketogenic diets may be helpful for people with special problems. This is a pretty weak statement and hard to disagree with.

6. A lowcarb, high fat diet doesn’t have to have a lot of animal products or a lot of protein in it. Yes. I am not a vegan, but I only eat a modest amount of animal products. (See “My Giant Salad,” “Our Delusions about 'Healthy' Snacks—Nuts to That!” “Intense Dark Chocolate: A Review,” “In Praise of Avocados” and “Eating on the Road.)

7. We should invest more in nutritional research. Here I love this sentence from the article: “Currently, the United States invests a fraction of a cent on nutrition research for each dollar spent on treatment of diet-related chronic disease.” Two weeks ago, I gave my own version of this argument:

To distinguish between different hypotheses, we need a lot more dietary clinical trials. Given the trillions of dollars worth of harm from the typical American diet (a number I discuss in “The Heavy Non-Health Consequences of Heaviness”), our nation is being penny-wise and pound foolish by not spending more money on dietary clinical trials to figure out what is healthy and what isn’t. Email correspondence with the head of one major study (see “Why a Low-Insulin-Index Diet Isn't Exactly a 'Lowcarb' Diet”) suggested that a reasonably high-quality dietary clinical trial (by current standards), might cost about $8 million. Thus, even without any government assistance, any billionaire could likely do trillions and trillions of dollars worth of good for the world by funding over time the equivalent of 100 dietary clinical trials of that size to test hypotheses about diet and health like those I discuss on this blog (and still have$200 million left over to live on). Some of this is happening, but much, much more needs to be done.

What is missing from this article is any discussion of the timing of eating. Fasting—periods of time with no food—is looking very promising in many studies as a way to gain many health benefits. (See “Stop Counting Calories; It's the Clock that Counts” and “Lisa Drayer: Is Fasting the Fountain of Youth?”) Even among readers of this blog, I have the sense that many think my main recommendation is to eat low on the insulin index. There is some truth to this, as you can see from “Obesity Is Always and Everywhere an Insulin Phenomenon” and “Forget Calorie Counting; It's the Insulin Index, Stupid.” But I consider fasting as the most important measure I would recommend for improving health through diet. Indeed, fasting is so important that I consider the single greatest benefit of a low-insulin-index diet to be that—in my experience and that of others I know—it makes fasting much easier. That is a claim I would love to have subjected a clinical trial.

On fasting, let me try to pull you away from some weirdnesses out there. In “Biohacking: Nutrition as Technology” I write:

Fasting doesn’t need any particular pattern. The environment of evolutionary adaptation for humans likely had a lot of random involuntary fasting. So we are likely to be designed for patternless fasting. The main thing is to (a) do enough total fasting and (b) fast for some reasonably long chunks of time, and (c) work up slowly to anything more than 24 hours so that you know your tolerance for fasting. That’s it. No particular pattern needed. Do a water-only fast (or allow unsweetened coffee and tea) when it is most convenient, which might be either when you are especially busy or when you have many distractions to keep your mind off of food (which could happen at the same time).

One sign of this weird, overly structured approach to fasting is the common phrase “intermittent fasting.” To me, the word “intermittent” here is redundant. If you don’t intersperse periods of eating food into your fasting, you will die! It is as simple as that. So I don’t think much of anyone is recommending non-intermittent fasting. Given that, one can call “intermittent fasting” just “fasting.”

I am not saying not to have any pattern to your fasting, but choose a pattern yourself based on what is convenient and requires the least willpower. I tend to fast on busy days when I have too many other things on my mind to think much about food anyway.

One thing I have been pleased at is that many clinical trials seem to be getting done about fasting. I would love to be involved as one of the scientists for one of those clinical trials. But in any case, we will know a lot more about the health effects of fasting ten years from now than we do today—both about safety and efficacy in improving health. To me, the evidence as it stands today makes fasting look like a good bet for your health.

Don’t miss my other posts on diet and health:

I. The Basics

II. Sugar as a Slow Poison

III. Anti-Cancer Eating

IV. Eating Tips

V. Calories In/Calories Out

VI. Wonkish

VIII. Debates about Particular Foods and about Exercise

IX. Gary Taubes