September 2017 Issue
Ask the Expert: Ketosis for Weight Loss
By Toby Amidor, MS, RD, CDN
Vol. 19, No. 9, P. 12
Q: I've been hearing a lot of buzz about people going on a ketogenic diet so they can lose weight. Is there science to support this?
A: There's science for and against following a ketogenic diet for weight loss, and the long-term effects on the body and weight maintenance are questionable. I spoke with two RDs who explained their stance on this debate.
Ketosis is a metabolic adaptation that has allowed humans to survive during periods of famine. When the body's glycogen stores are depleted, the body breaks down fat and produces ketones, which provide energy for the brain when glucose is scarce. Ketosis can be achieved either by fasting or by strictly limiting carbohydrate intake to less than 20 to 30 g per day. Fat is increased to about 70% to 80% of total calories, and protein intake is moderate.
The ketogenic diet has been used in children with epilepsy but recently has become trendy as a weight loss diet and parallels the popularity of the Atkins diet in the 1990s. Some followers of a ketogenic diet are seeking approval to eat hefty amounts of bacon and mayonnaise, while others seek to eat fewer processed and sugary foods. However, for years RDs have known the dangers of being in a state of ketoacidosis, says Felicia D. Stoler, DCN, MS, RDN, FACSM, FAND, who advises against following a ketogenic diet for weight loss. "In the clinical setting, health care professionals work very hard to control lab values," Stoler says, "and blood sugar, insulin, and ketoacidosis are some parameters closely monitored."
A 2014 review discusses the science behind the safety concerns of following a ketogenic diet. There's a lack of research on the long-term effects of a ketogenic diet in humans. As such, there's concern of the effects on renal function, as high levels of nitrogen excretion during protein metabolism can cause an increase in glomerular pressure and hyperfiltration.1 Furthermore, bone metabolism is a possible consequence of long-term adherence to a ketogenic diet; in children with intractable epilepsy, the diet may lead to reduction in bone mineral content.2
Conversely, Kristen Mancinelli, MS, RD, author of The Ketogenic Diet: The Scientifically Proven Approach to Fast, Healthy Weight Loss, is an advocate of ketosis for weight loss. "The unique benefit of ketosis is that it promotes significant weight loss because the body is constantly breaking down stored fat to meet its energy needs," says Mancinelli, who recommends exercising regularly and limiting calorie overconsumption while following this diet. "Ketosis dramatically diminishes hunger—another boon to weight loss that's unique to ketosis, so overconsumption tends not to be a problem."
Consumers already are confused about nutrition information, and conflicting RD recommendations make it even more confusing for them. Until long-term effects have been studied, RDs should be wary about recommending ketosis as a means for weight loss. Ultimately, it's a restrictive diet plan limiting fruits, vegetables, and fiber-filled foods, all of which provide health benefits.
There are clients, however, who will insist on following a ketogenic diet. Stoler suggests assessing the clients' knowledge base and motivation for doing so. "My style of diet planning is about lifestyle and feeling that food choices are not restricted," says Stoler, who's a firm believer that all foods can fit into a diet plan in moderation.
RDs must keep in mind that if a client is set on following a strict ketogenic diet to go into a state of ketosis for weight loss, nutrient insufficiencies can result. For this reason, Mancinelli recommends a multivitamin and mineral supplement that contains electrolytes, such as sodium and magnesium, and some B vitamins, all of which may be deficient in the diet.
— Toby Amidor, MS, RD, CDN, is the founder of Toby Amidor Nutrition (http://tobyamidornutrition.com) and the author of the cookbook The Greek Yogurt Kitchen: More Than 130 Delicious, Healthy Recipes for Every Meal of the Day and her newly released The Healthy Meal Prep Cookbook. She's a nutrition expert for FoodNetwork.com and a contributor to US News Eat + Run and MensFitness.com.
1. Paoli A. Ketogenic diet for obesity: friend or foe? Int J Environ Res Public Health. 2014;11(2):2092-2107.
2. Bergqvist AG, Schall JI, Stallings VA, Zemel BS. Progressive bone mineral content loss in children with intractable epilepsy treated with the ketogenic diet. Am J Clin Nutr. 2008;88(6):1678-1684.