Dear Alice,

I've been hearing a lot on fitness forums about the "keto diet." I don't know that much about it, but it sounds like it's a diet that's extremely low-carb and high-fat. People say they're getting great results by combining keto with exercise, but I don't understand how. Is there any science to support low-carb/high-fat as a good diet plan, or is this a fad?

Dear Reader,

Just like fashion fads on the runway, fitness and diet fads will come and go. It’s smart to ask questions about any diet plan or exercise regimen to help separate fact from fiction, so kudos to you for seeking out additional information! Originally, ketogenic nutrition strategies were developed for treatment of seizure disorders in children and adolescents. The use of the “keto diet” (originally known as the ketogenic diet) as a weight loss strategy is relatively recent. And as far as shedding pounds is concerned, the keto diet seems to be most effective in the short-term, especially when combined with exercise. However, this diet is also associated some health risks — so it’s good to explore the benefits and potential drawbacks in tandem.

Your initial conclusions about the keto diet are correct — the structure is based on an extremely low-carbohydrate, high-fat, and high-protein ratio of calorie sources. The keto diet plan follows a strict regimen of high fat, high protein, low carbohydrate food sources. Your body, in response to obtaining calories primarily from fat and protein, works to break down fatty acids for fuel. In contrast, a diet high in carbohydrates primarily relies on glucose (sugar) for energy. Maintaining adequate blood sugar levels, or levels of glucose in the blood stream, help ensure your brain has enough fuel to work normally. When glucose is not readily available, your brain can use ketones for energy. The process of burning fatty acids for energy is called beta-oxidation, and produces a byproduct — the ketone molecule. The keto diet is based off of this switch from glucose fuel to ketone fuel. When your body is burning primarily fat, and not glucose, ketones are produced in excess.

As far as an effective weight loss strategy, the keto diet typically has the most dramatic results within the first four to six weeks due to the dramatic changes in eating habits. Current scientific research on the keto diet shows that those using this plan specifically for weight loss may experience moderate or significant weight loss in the beginning weeks, followed by less dramatic results in subsequent months. According to some reports, individuals who follow a keto diet for eight to twelve weeks may see an additional reduction in body fat. Of the literature available, most sources advise using the keto diet under the supervision of a health care professional because of the restrictive nature and potential side effects.

Additionally, some people find these types of diets challenging to maintain long term because of how strict the rules are around what you can and cannot eat. Depending on where you read about the keto diet as a weight loss tool, you’re likely to hear varying reports of effectiveness. While initially successful with weight loss goals, over time issues like depleted energy, food cravings, and other side effects may hinder continued ability to adhere to the diet. Given the specific guidelines of the keto diet, it may be harder to get a diversity of important vitamins and nutrients from food. Many health care professionals advise incorporating a multivitamin into your diet. Dehydration, constipation, and development of kidney stones are also possible side effects of the keto diet. Some initial research on long-term use of the keto regimen shows potential risks of developing insulin resistance and developing diabetes. Use of the keto diet may also lead to elevated cholesterol or unhealthy amounts of fat in the liver. And if the ketones build up in your body quickly and you can’t excrete them through the urine fast enough, you can drastically alter your blood pH, which can be fatal.

You also asked about results due to the combination of the keto diet and exercise. Historically, there have been mixed conclusions in research studies about whether combining the ketogenic diet with exercise provides faster weight loss results or impacts athletic performance. The most recent studies seem to imply that keto plus exercise may cause the body to burn fat for energy without negatively affecting athletic potential. That said, some study participants did show elevated blood fat levels, which could increase cardiovascular disease risks.

Want to figure out if the ketogenic plan is right for you? It might be best to consult a health care provider to avoid any potential health consequences and also to tailor the program to your needs. If your goals are weight loss, there are many ways to achieve sustainable, healthy results. You may want to browse the Go Ask Alice! weight loss or fitness archives for some additional ideas.


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