Evidence-based Nutrition Information: Dr Michael Greger

I highly recommend Dr Michael Greger’s website http://www.nutritionfacts.org for evidence-based information on nutritional topics.

Dr. Michael Greger

There is a lot of nutritional information out there on the web and in books, and much of it is very scientific sounding. But as I’ve explained previously, for it to be really scientific, there has to be evidence to back it up. That’s why recently the term “evidence-based” has started being used. The best source I’ve found for evidence-based nutritional information is Dr. Michael Greger’s website www.nutritionfacts.org. He and his team of nonprofit helpers comb thousands of articles each year in the scientific literature for information related to nutrition. In his blog and in videos on the website, Dr. Greger never makes any claims without scientific evidence to back them up. One of his favorite sayings about nutritional claims or hypotheses is “you never know, until you put it to the test”.

I first learned about Dr. Greger and his website from reading his excellent book How Not to Die which is where I first found out about the whole food plant based diet. Some may claim that Dr. Greger is biased towards whole food plant based nutrition, but that is because he believes that way of eating is simply supported the best by the evidence. He is also pretty pragmatic in his definition of “whole foods”, leaning more towards “minimally processed”. He considers frozen fruits and vegetables to be perfectly healthy, for example. I find his videos and blog posts entertaining, and explained well in layman’s terms.

The Keto Diet and the “Carbohydrate-Insulin” hypothesis

A very important topic Dr Greger has covered recently in a series of videos is the ketogenic (or “keto”) diet:

Is Keto an Effective Cancer-Fighting Diet?

Keto Diet Theory Put to the Test

Keto Diet Results for Weight Loss

Are Keto Diets Safe?

Keto Diets: Muscle Growth & Bone Density

Does a Ketogenic Diet Help Diabetes or Make It Worse?

The keto diet is highly popular nowadays, to the point where grocery stores put “keto friendly” labels on foods, and even tout it as a healthy eating choice. The main reason keto is popular appears to be that it can deliver rapid weight loss. It is claimed it also leads to rapid fat loss.

While proponents of the keto diet cite evidence that it appears to be healthy in the short term, Dr Greger’s videos show that there are deleterious long term consequences of being on keto, like cardiovascular issues, bone loss, muscle loss, inflammatory effects, and various consequences of nutrient deficiencies. He also shows that keto is effective for treating type II diabetes, but only if you stay on it long term. It addresses the main symptom of diabetes, chronically high blood sugar, by keeping your blood sugar low since the carb level in your diet is so low. But it actually makes the cause of type II diabetes, insulin resistance (which is equivalent to carbohydrate intolerance) worse. So if you are diabetic and on the keto diet, and ever go off it by starting to eat more carbs, your symptoms will come roaring back.

Most interesting to me was the video Keto Diet Theory Put to the Test. This examines the claim that keto will deliver more rapid body fat loss.This was categorically proven false, in what I believe is a landmark scientific study [1]. Patients in a metabolic ward study, the most accurate kind because you control there food intake and can accurately measure body fat loss, were put on a control diet for one month followed by the keto diet. The control diet was moderate carb (50% carb, 15%protein, 35% fat). The keto diet was 5% carb, 15% protein, and 80% fat. Calories on the two diets were the same, as was protein intake. When they switched from the control diet to keto, their rate of fat loss was cut approximately in half. And they lost more muscle mass. This underlies one of the most important claims about the keto diet, that it turns you into “a fat burning machine”. You may become good at burning all the fat in your diet, but you actually burn less of your body fat.

Being in ketosis does suppress hunger, which is why people can lose significant amounts of weight on the diet. But the keto diet is known to have poor long term adherence. This sets it up to be a likely candidate for yo-yo dieting: you lose weight and aren’t hungry while you’re on it, but have trouble staying on it. When you fall off it and start eating more carbs, it has actually made your carb intolerance worse, as we saw above, and you are likely to overeat and gain the weight back. It is possible to lose weight on keto, then slowly and carefully reintroduce carbs, emphasizing good carbs and minimizing bad carbs. But that is not what most people do. When you are on any kind of restricted diet there is a strong psychological tendency to make a beeline back to your old favorites you’ve been denying yourself, which for most people includes bad carbs.

Avoiding processed foods and sticking to high fiber whole foods also reduces hunger. In my opinion that is a healthier and more sustainable approach to weight loss.

References

  1. Hall, K, et al, “Energy Expenditure And Body Composition Changes After An Isocaloric Ketogenic Diet In Overweight And Obese Men”, American Journal of Clinical Nutrition, 2016.

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