ASU nutritionist explains the popularity — and science — behind the keto diet.
August 2, 2017

ASU nutritionist weighs in on why the diet is so popular and how it works

Models, athletes and celebrities swear by the ketogenic “keto” diet to help shed those unwanted pounds. The keto diet encourages eating more cheese, butter and bacon; it’s a low-carb, high-fat diet akin to the Atkins Diet created in 1972 by cardiologist Robert C. Atkins. The latest fad diet has amassed a following of devoted supporters, including Tim Tebow, LeBron James and Kim Kardashian, but does it really work? 

Carol Johnston, professor and associate director of the nutrition program in the School of Nutrition and Health PromotionThe School of Nutrition and Health Promotion is part of the College of Health Solutions. at Arizona State University, explains why the low-carb, high-fat diet is so popular, how it works, and what dieters should be eating to lose weight. 

Question: Does the science behind the keto diet make sense? Would nearly eliminating carbs while increasing fat consumption help a person to lose weight? 

Answer: The short answer is yes. There is mounting evidence that suggests calorie restricted, low-carbohydrate, high-protein diets are effective for weight loss, and the keto diet is an extreme version of this. Low-carb diets can be more satiating, allowing dieters to feel full longer, eat less, and thus experience greater weight loss success. However, calorie restricted, high-carb diets are also effective for weight loss. 

Overwhelmingly, the most important factor in weight loss success is diet adherence. In research trials, most individuals who lose weight regain most of it within a year, regardless of which diet they were on. The downside of many of the fad diets you see today is the lack of emphasis on long-term lifestyle changes, which is necessary for long-term weight loss success. 

Q: In your opinion, why is this diet so popular? 

A: The keto diet is popular because it is easy to follow and on the surface seems effective. In the first few days after starting the keto diet, a person can experience a significant loss of water weight. When carb intake is restricted for a few days, glycogen stores in the muscle are reduced. Glycogen is responsible for water retention, so when its levels fall, so do our water levels. To the average person, the diet appears to be working. The number on the scale is going down. But, since most of this weight lost is water weight, it will return when the person consumes carbs again. While most people rely on scales to monitor weight loss and think any weight loss is good, the goal is actually to lose fat, which isn’t always reflected on the scale. Additionally, the elevated levels of satiety — feeling full — may help people stick to the diet longer and experience greater weight loss success. 

Bacon
The keto diet encourages eating more cheese, butter and bacon.

Q: Is the keto diet healthy? 

A: Keto diets have safely been used as an effective therapy for epilepsy for years. There are some risks associated with an extremely low-carb, high-fat diet, including elevated blood triglycerides (linked to elevated cardiovascular risk), increased urinary uric acid (which may lead to the formation of kidney stones), and lethargy. Adults on a low-carb diet are also at risk for adverse impacts to their bone health. 

Q: We’re always hearing about the evils of carbohydrates when it comes to losing weight. How important are carbs to our health and what role do they play in weight loss? 

A: Carbs play a critical role in our health. We get energy either by burning glucose from carbs, or by burning fat. The keto diet focuses on the latter. Though carb-restricting diets are popular, carbs are actually less likely to convert into body fat than dietary fat. 

Carbs are important for our brain and muscle health. Our brains rely entirely on glucose for energy production — they can’t get it from fat — making the consumption of some carbs necessary. Our muscles can use either glucose or fat for energy, but during high-intensity exercise, they prefer glucose. 

When we eat more carbs than we need, they convert to body fat, which contributes to obesity. In general, average Americans — those with a relatively sedentary lifestyle — consume more carbs and calories than they actually need. Athletes, on the other hand, need to keep their carb intake elevated to support their energy output. Balance between energy intake and output is key to maintaining a healthy weight. 

Q: For people who are trying to lose weight — what foods should they avoid? What foods should they include in their diet? 

A: Energy-dense foods should be avoided (gravies, dressings, sauces, sweets, pastries, cakes, cookies, sugary drinks, etc.) and low-energy, nutrient-rich foods should be prominent in the diet (unprocessed plant foods, low fat dairy and lean, unprocessed meats). 

Q: What should people know about the effectiveness or safety of fad diets like Atkins, keto, liquid diets, paleo, calorie restriction, etc.? 

A: Any diet that restricts calories will typically result in weight loss if a person sticks with it. What is important when following a calorie-restricted diet (about 500 less calories per day) is that it has healthful attributes — a diet composed of plant-based, unprocessed foods with low fat content — such as the Mediterranean diet. (Note, 500 calories equates to two 12-ounce sodas and a large chocolate chip cookie!) 

 

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