So many of us have a few extra pounds to lose, and lately two ways of eating have earned a lot of attention for their ability to help followers slim down fast: the keto diet and intermittent fasting.
Both approaches to eating can help you drop weight quickly and may offer additional health benefits. But what about combining the two?
What Is Keto?
Cathy Leman, a registered dietitian nutritionist and founder of Dam. Mad. About Breast Cancer, a nutritional consulting firm based in greater Chicago that’s aimed at helping breast cancer patients and survivors, explains that a classic keto diet is a “high fat, adequate protein, low-carbohydrate diet designed to produce ketosis through mimicking the metabolic changes of starvation. Keto diets force the body to use fat as its primary source of energy.”
The keto diet has been around since the 1920s, first developed to manage seizures in children with epilepsy, says Kacie Vavrek, a sports dietitian at the Ohio State University Wexner Medical Center, in Columbus. While there’s ample evidence that the diet can be a life-changing intervention in some individuals with epilepsy that don’t respond to other treatment interventions, “we do not have evidence that keto is effective or safe long term for anything other than epilepsy.”
Nevertheless, over the past few years, the keto diet has gained a staunch following as a means of rapid weight loss, and some people have suggested it could help manage certain chronic diseases such as diabetes. Vavrek notes that “cutting back on low quality carbs like sugar and refined flour is good for everyone,” and this is part of the upside of the keto diet. “However, keto also cuts out healthy, high-fiber foods like fruits, whole grains, beans and lentils and starchy vegetables that are important for overall health and gut health.”
And, while some people do drop a significant amount of weight quickly while following the keto diet, not everyone does. Liz Weinandy, a registered dietitian also with Wexner, says that “many people gain weight from it is since it is a very high fat diet and fat is very high in calories.” And weight loss success may be difficult to maintain long term. For many folks, as soon as you loosen up some of the restrictions, the weight comes back quickly.
Similarly, there’s not enough information about the long-term benefits of the keto diet in preventing or managing chronic diseases such as heart health and diabetes. This is in part because of “the extreme difficulty with staying on this type of diet long term,” Vavrek says. Also, the diet “can be very high in red meat, salty foods, processed foods and saturated fat,” which are antithetical to overall good health.
In fact, Vavrek says following a strict keto diet “can lead to kidney stones, constipation, nutrient deficiencies and possibly an increased risk of heart disease. Keto can improve blood sugar levels in the short term, but long-term research is limited.”
The keto diet ranked No. 34 (out of 35 diets reviewed) on U.S. News’ list of Best Diets Overall. It tied for No. 3 on the Best Fast Weight-Loss Diets ranking and No. 15 on the list of Best Diets for Weight Loss.
What Is Intermittent Fasting?
Intermittent fasting is a pattern of eating that cycles through periods of eating and periods of fasting. It’s not a diet that dictates what you can or cannot eat, rather it shifts when you eat. Some of the more common approaches include:
— The 16/8 method. This involves a 16-hour fast followed by an 8-hour window when you can eat.
— The 14/10 method. This follows the same idea as the 16/8 method, but is slightly less limiting and may be easier for beginners to get the hang of fasting. You fast for 14 hours and have 10 hours to consume your daily calories.
— The 5:2 diet. In this approach, you’ll eat normally five days of the week but then limit your calorie intake significantly — consuming only about 500 or 600 calories — two days of the week.
— Eat-stop-eat, AKA the 24-hour fast. This approach is similar to the 5:2 diet, but instead of consuming just a few calories on those two fasting days, this approach calls for a 100% fast during those two 24-hour sessions each week. Some versions of this approach call for just one day of fasting per week instead of two.
— Alternate-day fasting. In this approach, you’ll alternate a 24-hour fast or severely restricted calories and a normal diet every other day.
— Spontaneous meal skipping. In this approach, you don’t follow a rigid plan, but simply skip meals now and again when you’re not hungry or don’t have time to prepare a meal.
Like keto, intermittent fasting can also be a restrictive approach to food, but it may be a little easier for some people to follow because it doesn’t specifically limit the foods you eat, just when you eat them.
“Intermittent fasting can be beneficial for controlling calorie intake when done correctly,” Vavrek says. “Limiting eating to a specific window can prevent overeating in some people.”
However, it’s not without risks. It can “end up being too restrictive and result in starvation dieting,” Vavrek says. “When a diet is too low in calories, it can lead to muscle and water losses, as well as nutrient deficiencies. These extremely low-calorie diets often result in decreases in metabolism which lead to weight gain in the long-term.”
As with keto, the jury is still out on whether there are long-term health benefits to intermittent fasting. “Small studies have found lowered blood sugar, blood pressure and cholesterol in short-term studies, but we do not have enough research to support this diet for long-term health benefits,” Vavrek says.
The Fast Diet, which ranked No. 29 on U.S. News’ List of Best Diets Overall, is based on the 5:2 approach to intermittent fasting. It tied for No. 21 in the Best Fast Weight-Loss Diets ranking and No. 28 in the Best Weight-Loss Diets ranking.
Can I Do Both Keto and Intermittent Fasting Together?
Using an intermittent fasting approach to a keto diet might offer a few benefits, such as helping you achieve ketosis faster. Ketosis is when the body is burning fat for fuel in the absence of adequate carbohydrates. It’s the hallmark function of the keto diet, and it can be a feature of intermittent fasting, depending on which approach you take.
If you follow a strict ketogenic diet, your body will reach a state of ketosis, so you don’t have to do both together. You just might get into ketosis a little faster if you’re also fasting intermittently while following a keto diet.
Despite this potential speed advantage, Vavrek doesn’t recommend following a keto diet while also fasting intermittently. “Both diets can be very restrictive, and restrictive diet plans do not work long term and can result in negative health outcomes as well as muscle loss and decreased metabolism. Active individuals and athletes especially may find it difficult to fuel and refuel for an active lifestyle on these diet plans.” And there’s some indication that “these types of diet plans often lead to yo-yo dieting, which has been linked to increased mortality.”
However, she adds that “both of these diets can be done in a healthful or modified way,” and aiming to manage your weight with a less restrictive plan might end up being better in the long run. “A modified keto diet that allows for healthy carbohydrate foods like fruits, starchy vegetables and whole grains might be a better option” than a classic keto approach. “You might be better off following a balanced diet in the correct calorie range for your specific goals,” Vavrek says.
To figure out the best calorie range and eating plan for you, consider working with a registered dietitian who can look at your entire health picture and goals and formulate a tailored recommendation for sustained health and well-being.
And lastly, Vavrek says it’s important to “ask yourself what your health goals are and why you feel that you need to follow a restrictive diet to meet those goals. Almost all health and weight goals can be met with a healthy balanced diet.”
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Can You Do Keto and Intermittent Fasting Together? originally appeared on usnews.com