BIG Nutrition: The Keto Diet—The good, the bad, and the ugly!


BIG Nutrition: The Keto Diet—The good, the bad, and the ugly!

This year’s most popular diet is the Keto diet. Keto is short for ketogenic, a diet that relies on a body pathway, ketosis, for burning fat for fuel. As an effective diet therapy needed for individuals with inborn errors of metabolism and severe epilepsy, the diet is getting a fresh look for the potential to burn body fat and promote weight loss. The Harvard Public Health Newsletter has a terrific review on the topic.

The diet omits all sugar, grains, rice, beans, lentils, fruit, and potatoes and other starchy vegetables and permits eating meat, fish, nuts, seeds, non-starchy vegetables, and fat (for example, olive oil and avocado). For those who follow macros, the carbohydrate intake is restricted typically to ~10% of total calories or less from carbohydrate (50 grams less/day), 15-20 % calories from protein, and 70-85% calories from fat.

With limited research for the use of the diet in healthy persons, here is what is being learned:

The Good

  • Fat is satiating, so some people experience less hunger; however, this is not a consistent finding.
  • Decrease in circulating insulin levels.
  • Burn more calories as fat is converted into glucose, the brain’s fuel.
  • Body fat loss, at least in the short-term.

As with most diets, which tend to happen short-term, there can be weight loss with omission of foods that are part of a person’s typical intake, such as, refined carbohydrates and alcohol. Studies looking at long-term results have not found the ketogenic diet to be better than other diets at one and two years.

The Bad

  • It takes the body at least 3 weeks to adapt to the diet.
  • Exercise intensity may be decreased so this is not for competition time or when higher intensity exercise is needed.
  • ‘Brain fog’ as the body adjusts to converting fat to glucose.
  • Tiredness, moodiness.
  • Constipation if there are not enough vegetables consumed.
  • Omission of key nutrients, but with the assistance from a dietitian nutritionist fewer nutrient deficiencies are possible.
  • Difficult to do over the long run because of the multiple restrictions.

The Ugly

  • There is not much research on use or safety for healthy people, pregnant or lactating women, or children. There is a small amount of research in elite athletes, but it is not clear if this is applicable to non-elite athletes.
  • While weight loss may be helpful for those with diabetes or cardiovascular disease, only small studies have looked at the cardiovascular impact of this high fat diet with conflicting results. In the research that shows improvement in lipid levels, this may be due to a proportional higher intake of unsaturated (olive oil, avocado) verses saturated fats (meat, bacon). Most of the studies are of short duration, so it is not clear if benefits persist.
  • Potential risk of kidney stones and osteoporosis.
  • Omission of nutrient components that are not in vitamin/mineral supplements

If thinking about testing this diet out, consider the evidence before jumping in. Just as important, consider what to do after the diet.

Happy and healthful eating,

Donna G. Pertel, MEd, RD, LDN

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