Ups and Downs of a Ketogenic Diet

At first glance, the ketogenic diet looks more like a diet of indulgence than deprivation: Eat high-fat foods like bacon, eggs, cheese, nuts, butter and oils and don’t worry about counting calories.

“This is the new fad diet that everyone wants to try,” says Premier Health dietitian Meredith Jones, RDN, LD. “People think they’ll lose weight fast eating yummy, high-fat foods.”

The theory behind the ketogenic diet is to cut carbohydrates to about 20 to 30 grams per day, generally in the form of vegetables. Carbs usually provide the fuel your body uses to create energy. With a drastic reduction in carbs, your body looks for an alternate source of energy. It starts breaking down stored fats carried to the liver to make a byproduct called ketones, which become the new fuel for your brain and body.

"If you want long-term weight loss, you want a long-term diet with healthy eating and exercise.”

There is some quick weight loss from burning fat to make ketones, but Jones says it’s not likely that a person can sustain this diet long term. Once you re-introduce carbohydrates into your diet, your body will use those as your primary source of energy. People often gain back the weight they’ve lost. 

Although the keto diet can lead to short-term weight loss and tends to curb hunger, Jones notes potential drawbacks:

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  • Initially, the changes in how your body produces energy can cause flu-like symptoms called “keto flu.” Jones notes, “You can feel groggy, achy, headachy and lethargic for a few weeks, and you have to suffer through that before you feel normal.”
  • In extreme cases, people who make too many ketones develop ketoacidosis, a condition in which the blood becomes too acidic. This can be toxic and even deadly.
  • A lack of carbohydrates may cause deficiencies in fiber, iron, calcium, magnesium, folic acid, vitamins C and D, and thiamine (vitamin B1).

Cautions and Alternatives

Jones says claims that the diet may lower cholesterol levels are inconclusive. “There have been some studies that show improvement in cholesterol levels, but that may just be for the first six months,” she says. “Follow-up in a year or two shows there doesn’t seem to be a benefit. When anyone loses weight by any means, it will improve their lipid profile. So, it’s hard to discern whether it’s the actual keto diet or the weight loss.”

Jones cautions against trying the keto diet if you are pregnant, nursing or have certain medical conditions. “Don’t try this diet if you have liver disease, because it taxes the liver. It’s not good for people with kidney disease, because your body will have trouble ridding itself of ketones. And people with type 2 diabetes need to be careful about taking medicines that lower blood sugar, which will already be low from a lack of carb intake.”

In general, Jones doesn’t advise eliminating entire food groups from your diet. For people who have a lot of weight to lose and want to jump-start their diet or try something new when everything else has failed, Jones strongly recommends checking with your primary care doctor first. 

“Explore other options that are healthier and better for long-term weight control,” Jones counsels. For weight loss and cholesterol lowering, she recommends a heart-healthy diet, Mediterranean diet or even a plant-based diet that allows some meat. 

“You don’t want to risk your gut’s health, vitamin deficiency, or the yo-yo effect of losing weight and then gaining it back when you go off the rigid diet. If you want long-term weight loss, you want a long-term diet with healthy eating and exercise.”

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Meredith Jones, RDN, LD

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