Nutrition
What are the differences between popular low-carb diets?
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- Reviewed by Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
Q. If a person wants to try a very low-carb diet, what's the difference between a carnivore diet, a keto diet, and a paleo diet?
A. While all three diets are low in carbohydrates, there are significant differences in what each contains.
Ketogenic (keto) diet. A "true" keto diet does not provide enough calories from sources of glucose and other forms of sugar and causes the body to burn fat to create energy. When fat is broken down, ketones are released by fat cells into the bloodstream. The increase in blood ketones lowers the normal acid-base balance in blood to make it more acidic, a state known as ketosis. In a typical keto diet plan, approximately 70% to 75% of daily calories come from fat, 20% from protein, and no more than 10% from carbohydrates. The food and beverage choices to provide this caloric mix can vary.
Carnivore diet. A carnivore diet is the most ketogenic because its carb content is extremely low, which is why it's sometimes called the "zero carb" diet. You only eat meat, poultry, eggs, fish, and dairy. The long list of foods not allowed includes all vegetables, fruit, grains, legumes, seeds, and nuts.
Paleo diet. The paleo approach centers on the unprocessed, truly natural foods humans consumed through hunting and gathering in the Paleolithic era, which ended about 10,000 years ago. The food choices can come from meat, fish, poultry, eggs, vegetables, fruits, and nuts. Any refined or artificial products (including healthy oils like olive oil), dairy, grains, legumes, and potatoes are excluded because they appeared after the agricultural revolution that followed the Paleolithic era. A paleo diet can be ketogenic if simple carbs are limited enough. Still, you can go paleo and not be in ketosis by eating more fruits, especially berries.
So, which of these three approaches, if any, might you consider trying? The pros and cons of a keto diet depend on your goal. If you want to jump-start a weight-loss program, a keto diet can help you lose five to 10 pounds or more. The downside, even for the short term, is a potential rise in LDL (bad) cholesterol. Personally, I have concerns about staying in ketosis for more than four to six weeks. Longer-term use of a keto diet is linked to a higher risk of kidney stones, osteoporosis, and gout.
With the paleo diet, you have flexibility regarding being in and out of ketosis. However, because grains are not allowed, you would need to find ways to supplement your fiber intake. And you can miss some essential micronutrients.
Finally, given the overwhelming evidence supporting the benefits of a plant-based diet, I would never recommend a carnivore diet.
Image: © SewcreamStudio/Getty Images
About the Author
Matthew Solan, Executive Editor, Harvard Men's Health Watch
About the Reviewer
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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