Defining the keto diet

The ketogenic diet is a high-fat, moderate-protein and very low carbohydrate diet.  Generally we’re looking at 75% of calories from fat, 15-25% from protein and 5% from carbohydrates. Per the Mayo Clinic, “Getting most of your calories from fat forces your body to use different energy pathways. Instead of carbs for energy, the body burns fat, entering a state called ketosis.” People are drawn to it because it can lead to weight loss. According to Diet Doctor, here’s how to go about it:


  • Meat
  • Fish and seafood
  • Eggs
  • Natural fat, high-fat sauces
  • Vegetables growing above the ground
  • High-fat dairy
  • Nuts in moderation
  • Berries in moderation

Don’t Eat:

  • Wholegrain products
  • Legumes, such as beans and lentils
  • Fruit
  • Sugar
  • Starch

Well this is interesting…

The keto diet is practically the opposite of a plant-based diet! Have to love these conflicting messages about what to eat. Whenever I see this kind of thing, I just step back a bit and look at the big picture. We know that populations in the world living the longest, healthiest lives (see The Blue Zones) are eating a plant-based diet, which derives about 50% of calories from carbohydrates. And the World Health Organization (WHO) supports this with their definition of the healthy diet: fruit, vegetables, legumes, nuts and whole grains. Animal products are not on the list.

One of the likely reasons animal products are not part of the WHO’s healthy diet definition is that they are generally high in saturated fats. The WHO suggests that the intake of saturated fats be less than 10% of total energy intake. The keto diet strongly promotes the intake of food that is high in saturated fat. What’s the problem with saturated fats? The WHO based their recommendation, in part, on this Food and Agriculture Organization of the United Nations report, which concludes that there is convincing evidence that replacing saturated fats with polyunsaturated fats (found mainly in plant foods) decreases the risk of heart disease. This is important because heart disease is the leading cause of death globally, accounting for over 9 million deaths in 2016.

Let’s look at some low-carb data

The ketogenic diet has mostly been studied for the treatment of epilepsy. Otherwise, there are not yet a lot of published studies. However, there’s a government-funded, peer-reviewed study published in 2018 in The Lancet Public Health looking at the impact of carbohydrate intake on health. Refer to it here. It included a meta-analysis, which means it combined data from a group of comparable studies. From the data, the authors concluded:

  • Both high and low percentages of carbohydrate diets were associated with increased mortality, with minimal risk observed at 50–55% carbohydrate intake.
  • Low carbohydrate dietary patterns favouring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality, whereas those that favoured plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain breads, were associated with lower mortality, suggesting that the source of food notably modifies the association between carbohydrate intake and mortality.

The authors proposed the following possible reasons for the conclusions:

  • Low carbohydrate diets have tended to result in lower intake of vegetables, fruits, and grains and increased intakes of protein from animal sources
  • It is likely that different amounts of bioactive dietary components in low carbohydrate versus balanced diets, such as branched-chain amino acids, fatty acids, fibre, phytochemicals, haem iron, and vitamins and minerals are involved.
  • A low carbohydrate diet with low plant and increased animal protein and fat consumption may stimulate inflammatory pathways, biological ageing, and oxidative stress.

A sometimes inconvenient truth

For those of us who struggle to lose weight, the ketogenic diet may look very enticing. Indeed, we may lose weight, but the best available evidence indicates the healthiest approach to eating for the long term includes mostly plant-based foods, which are high in fibre, phytochemicals, vitamins and minerals. This study of 89,000 Californians showed that only the plant-based eaters (compared to vegetarians and omnivores) had a body mass index, on average, within the healthy range. I love how Kim Williams, MD, Chief of Cardiology at Rush University responded to the question of whether to follow a ketogenic diet: “Only do it if weight loss is more important than your life.”