The ketogenic diet is based on the basic idea that the body will always burn glucose (which breaks down from the carbohydrates) before it burns ketones (which are the breakdown of fat).
By replacing most of the carbs in our diet with fat, proponents say it can fast-track weight loss, curb appetite, treat various health ailments and increase athletic performance.
The diet originated in the 1920s as a treatment for epilepsy, but became trendy in the fitness industry among those trying to shed and shred. Celebrities such as Gwyneth Paltrow and Kim Kardashian also tried chewing the fat.
While the keto diet has been slammed as a fad and is known for its side effects including constipation and bad breath, new research suggests it can improve memory and lifespan.
In two new studies mice were fed either a ketogenic diet, a control diet, or a low-carb, high-fat diet (ketogenic is a more extreme version of low-carb and accounted for 89 to 90 per cent of total calorie intake in the studies) and put through tests of physical health, fitness and memory.
In both studies the keto mice lived longer and showed memory improvements, while only one showed maintenance of physical fitness and strength as mice aged.
For the benefits, however, there was a catch. Mice that stay on a keto diet eventually become obese. To avoid this the mice were cycled between regular diets and the keto diet.
“This study demonstrates that energy-controlled, high-fat LCDs are not detrimental to health, but rather a KD extends lifespan and slows age-related decline in physiological function in mice,” the study authors concluded.
“It is most probable that this approach could improve health outcomes, slow diseases of ageing and increase human lifespan,” said Brian J. Morris, an Emeritus Professor at the School of Medical Sciences and Bosch Institute, at the University of Sydney.
But experts also point out that the mice in the control diet were fed high-glycaemic carbohydrates that included a significant amount of sucrose.
“So is it that the low carbohydrate/ketogenic diet is relatively effective or is it that the ‘control diet’ is relatively adverse?” asked Professor Manny Noakes, the research program director for Nutrition and Health at CSIRO Health and Biosecurity.
“I might suggest the latter but at least there is an increasing research effort into understanding lower carbohydrate dietary patterns, which have been on the fringes in the scientific literature until now.”
Experts also point out that human studies of ketosis have been short-term because adhering to a keto diet for an extended period is extremely difficult.
Libby Babet, personal trainer on The Biggest Loser and owner of Sydney’s Agoga and BUF Girls, has tried the keto diet.
“I did it for short-term health wins and the outcome was more mental focus, calmer vibes and less anxiety … but less on the athletic performance side, no energy for workouts and I actually gained a little weight,” she says. She says it also required lot of focus on food.
“You literally can’t eat even veggie carbs other than leafy dark greens like spinach/lettuce if you want to stay in keto and even then you have to smother in olive oil or avocado so you don’t kick yourself out of keto! You also kick yourself out if you have too much protein,” Babet says.
“I do love and advocate healthy fats but don’t think a true keto diet is sustainable – or fun – for many people.”
The nutrition experts agree.
To maintain ketosis a human adult could only consume 20-30 grams of carbohydrates a day (one medium apple contains 20 grams of carbs, a corn cob has about 15 grams).
It is a dietary pattern that would lead to deficiency in vitamins and minerals “unless the diet is carefully constructed, and would usually require micro-nutrients and minerals to be provided by supplements”, said Professor Helen Truby, from the Department of Nutrition, Dietetics & Food at Monash University, Australia.
While the findings are “intriguing”, Truby says more research is needed to understand the diet’s mechanisms and despite its potential benefits – there is also interesting research about ketosis as a treatment for cancer and epilepsy – it is not for your average Joe.
“Should people start ketogenic diets? Answer: not unless there is a medical indication to do so and under the guidance of an accredited practising dietitian who can ensure nutritional adequacy,” Truby says.
“In terms of ketosis being the cure for memory loss, I doubt anyone would be able to stick to the sort of strict low-carb regimen necessary for long-term use and therefore its applicability to humans is currently limited by the unpalatability of the dietary pattern that is required.”