Are Keto Diets Good for Us?

**Michael Greger** (0:00)
I'm often asked my opinion about the cause or treatment of some medical condition, but the question to instead ask is what does the science say? What is the best available balance of evidence published in the peer-reviewed medical literature have to say right now? Welcome to the Nutrition Facts Podcast. I'm your host, Dr. Michael Greger. Today, we take a look at the popular keto diet, the high-fat, low-carb diet that puts the body in a metabolic state called ketosis. And we start with the effect of the keto diet on LDL cholesterol, with Dr. Dennis, our new Senior Research Scientist.

**Dr. Dennis** (0:38)
The effect of a plant-based, low-fat diet versus an animal-based ketogenic diet on caloric intake and weight loss. A plant-based diet without sugary refined grain foods versus a keto diet with a lot of vegetables. After two weeks randomized to one of the two diets, the participants were switched to the other one for another two weeks. Looking at the scale, guess who lost more body weight? Those on the low-carb diet. But guess who lost more body fat? Those on the low-fat diet. In fact, there was no significant fat loss on the low-carb diet, whereas two pounds of fat were lost on the low-fat diet. What they were losing on the low-carb diet was fat-free mass, like water weight but muscle too.
While fat-free mass was relatively preserved while on the low-fat diet, fat-free mass decreased on the low-carb diet. And there was evidence that participants were losing muscle mass despite eating more protein than when they were on the plant-based diet. But when they were eating almost no carbs, their blood sugars were certainly lower. Does a ketogenic diet have a place within diabetes clinical practice? It's even been suggested that low-carb diets could put type 2 diabetes into remission. Which can be defined as an HbA1c, a marker of blood sugar control, lower than 6.5% for at least three months after stopping any blood sugar lowering medications. But high blood sugars are just the symptom. The disease is one of carbohydrate intolerance. If you're allergic to peanuts and don't have symptoms because you avoid peanuts, you're just managing the disease, not curing it. Curing a peanut allergy would mean being able to eat peanuts like anyone without a peanut allergy. It's the same with carbohydrates and type 2 diabetes. True remission would be being able to eat carbohydrates like everyone else without getting adverse effects. As Dr. Greger has covered, low-carb diets can actually make diabetes worse, worsening insulin resistance and increasing intolerance to carbohydrates. That would only be a problem though if you resumed eating carbohydrates. Why not just stick to a ketogenic diet forever? What is the efficacy and safety of low-carb diets for type 2 diabetes remission? First of all, it didn't work. Using the under 6.5 percent and off all diabetes medications definition of remission, there was no significant effect at six months. At 12 months, there was less remission, meaning more diabetes in the low-carb groups. Along with clinically important harms on quality of life, and the DL killer, an increase in LDL cholesterol.
LDL cholesterol, commonly known as bad cholesterol, is unequivocally recognized as the principal driving force in the development of atherosclerotic cardiovascular disease, the leading cause of death for both men and women. Basically, we should try to get our LDL as low as possible. Lower for longer is better. Even if our LDL is normal, even if other heart disease risk factors are considered optimal, it is of utmost important to control our LDL. If LDL is the primary driver of our primary killer, then if we could just know one thing about a diet, if there were only one question we could ask about some new diet someone tells us about, it would be, what does this diet do to my LDL cholesterol? If you follow people on lower carb diets over time and see what happens to their coronary artery calcium scores, which signify the progression of coronary artery disease, you'll find that the low carb group had the highest incidence of coronary artery calcium worsening. But this was only the case with animal based low carb diets, not plant based ones. But those who started eating low carb diets rich in animal protein and fat in early adulthood, had an increased risk of coronary artery calcium progression in middle age. Of course, all carbs are not created equal. Carbs that are detrimental to our health, like sugars and refined grains, need to be distinguished from those with beneficial effects. When the American Heart Association looked at dietary patterns at a population level and ranked them from the most to the least aligned with its dietary guidance for heart health, how did low carbohydrate diets rank? Poorly. In fact, they were ranked the worst. Even when very low carb diets are followed optimally, they promote restriction of foods considered essential to heart health, like legumes and whole grains, and include high saturated fat sources like meat and dairy, which are both strongly discouraged.