A recent study has come out saying dietary fat is bad. There will probably be more coming that say dietary fat is bad and there have been many before that say that dietary fat is bad. I don’t believe them. I’ll tell you why.
Context: the Atkins diet
Years ago, I was introduced to this high-fat diet by a couple of my patients. (I’m an internist and I work at Duke University.) I was working at the Durham VA Hospital at the time and they did this very high-fat diet. It was called “Atkins” at the time. I didn’t know much about nutrition and I definitely didn’t hear of the Atkins diet before, but they did it and clearly lost weight. One of the gentlemen was eating steak and eggs pretty much all day; he said that’s all he ate. I thought to myself, “This goes against everything that I’ve been taught!” Remember, this for me is 24 years ago now, so like most doctors who hear about it now, they’re skeptical. They ask, “How can you eat all this fat? We know fat is bad.” I knew at least in this context of a weight loss diet, called the Atkins diet, that you could lose weight and all of the parameters also looked good. In fact, the cholesterol levels of these patients looked fine. I started doing research and the studies that we did were finding the same as what Dr. Atkins had found – not what other people had predicted. It turns out over the years that Dr. Atkins was right! At least in the context of insulin resistance, eating high-fat diets with low-carbs can be very healthy. That’s the first thing you need to know – what is the context of the statements, “High-fat diets are bad” or “Eating fat is bad”?
A generation of doctors was taught that eating fat is bad, without hard evidence of that happening. “Hard evidence” means prospective studies, clinical trials – the kind of research that you would expect before a drug company starts selling a product or marketing. In the U.S., they have to go through the hoops and do the clinical trials before a drug is allowed to be marketed. There are some regulations about what you can say about medications; there are no regulations about what you can say about food. It’s a sad state of affairs. I wish it wasn’t this way, but that’s the way it is.
The idea that fat in the diet was bad was not based on sound science by today’s standards. If you really want to deep dive into this, Gary Taubes’ first book on the topic, Good Calories, Bad Calories, went over all of the science in great detail up until about 2004 or so. Nina Teicholz also wrote a helpful book, called The Big Fat Surprise. These are both investigative journalists and it’s pretty amazing that these were non-scientists writing. It makes sense, because scientists get biased with a certain opinion of looking at things. Nina Teicholz’s book picks up the story and carries it forward to about 2010. If you want to read about the science of eating fat (and how the demonization of dietary fat is not solid), I refer you to those books.
Comparing low-fat and high-fat diets
I remember seeing the first paper at a meeting in about 2010 or so, where the research being presented was showing that eating fat was fine. It was going against all of the guidelines, and it was a well-respected group. They ended up doing what’s called a meta-analysis – a study of studies. One study might say eating fat is bad, another one would say it’s not bad, but you could line them all up and see what the averaging of all of these things was to get a better resolution of whether it really is bad. I was primed for the idea that eating fat might not be bad through scientific research around the year 2010.
Nutritional epidemiology is a weak science
Today, I see nutritional epidemiology, which is a “weak science”. It involves maybe asking someone what they’re eating, you follow them forward but you don’t go home with them and see what they actually eat. You don’t ask them what they’re eating very frequently and then you determine whether they have a problem or not. The issue with nutritional epidemiology is that you can often see what you want to see and measure things in ways that don’t help you tease out whether it was the carbs or the fats, for example. You might have a hamburger, which is called a high-fat food when actually there are carbohydrates in the bun. This is where, unless you’re doing a prospective study and really tearing apart what’s under the hood of what people are eating or even better yet, a study where you put people in a hospital or a residential area and feed them so that you know exactly what they’re eating, you really have to be careful about those studies where you’re getting what people tell you they’re eating (as opposed to what they’re really eating).
The definition of a low-carb diet in these nutritional epidemiology studies is most commonly under 30 percent of the total daily calories. To me, that still is a rather high-carbohydrate diet. You always want to look not at the percent of carbohydrates in the daily calories, but you want to look at the number of grams of carbohydrates in the diet of that individual or group. If you look at the grams of carbohydrates someone’s eating, 30 percent carbs, they might be eating 150 grams of carbohydrate. The powers that be are saying that’s a low-carbohydrate diet. That doesn’t separate out the people eating a low-carb diet – under 100 or under 50 grams per day – or the way I teach to get maximal fat burning, a keto diet is actually under 20 or 30 total carbs per day. These are all lumped together with people eating 150 grams per day. There are metabolic changes that occur in that area of going from 70, 60, 50, 40, 30, and 20 grams of carbs per day, including going into metabolic ketosis, which is maximal fat burning. There are also things that change in terms of inflammation. Ketones can have an anti-inflammatory effect, so to lump all of these people together is a mistake. It’s really not telling you the details about people who are eating what I teach.
Clinical trials reveal that eating fat is not bad
What I see from clinical trials going forward in obesity treatment and diabetes treatment and in clinical care, treating thousands of people at Duke University over the last 15 years in a clinical setting is that people get better, not worse. There’s a difference between 50 grams and 20 grams (of carbohydrate) per day, so to lump all these people together and say, therefore, low-carb is bad, is really a mistake. There are nuances. There are changes that are very different even from 100 grams a day to 50 grams a day to 20 grams a day. Beware or be forewarned now to always look at the methods section of a study. Be careful about just reading the title. People will see what they want to see. Even the methods in the abstract – often that’s all that’s provided for free – might not tell you the detail that you want to get to. When I see a research paper, I always go to that methods section first and see, “Well, how many grams were the subjects not only taught to have but how many grams of carbohydrates per day did they actually have?”
There’s one classic paper that’s cited all over, done at a major academic university in the U.S. They said that they taught people to eat a certain level of carbs but they didn’t achieve that in the methods. They didn’t actually get the subjects to eat that, yet they still called it a low-carb diet, even though they weren’t actually able to carry out what they intended to do. That’s why it’s really important to see what the actual carb consumption and fat consumption was.
Metabolic changes on a keto diet matter
The major metabolic change that’s happening is you’re burning fat. In a couple of papers that really should get more public attention, the more you go down on the carbs, the more your body’s burning fat. The fat in the bloodstream is lower even though you’re eating more fat. It’s because you’re burning it. The low-carb science is so strong now, there are so many clinical trials that the burden of proof is on the people who are saying that it’s bad, to prove it. Epidemiology studies and observational studies are not sufficient to show that these types of diets, which demonstrate a metabolic change, are bad. It would be like saying we studied everyone on earth and so therefore people on the moon are going to be behaving in a certain way, even though the gravity between the two is different!
The metabolic situation is very different on a keto diet. These other studies really don’t show that eating fat is bad. I’m going to say, “Prove to me with the people who are really eating a keto diet that a keto diet is bad and eating fat is bad.” Those studies don’t exist and I don’t think it’s going to happen – eating fat and eating low-carb isn’t going to be proven harmful – unless you’re doing a weird version of a keto diet. Be sure you’re getting great teaching, and follow someone who has done the diet for the same reason that you want to do it. Often you can get down different pathways because the person who’s teaching you didn’t have diabetes to fix or didn’t have a weight loss journey. Don’t fear eating the fat!
Check out the full video here.