Foundations of a Keto Diet

By Lucia Weiler RD PHEc for Made Good Foods

You’ve heard about the ‘Keto Diet’ and may even know people who tried it, but have you wondered what it really means?

The Keto Diet, also known as Keto or the Ketogenic diet, is a very low-carbohydrate and high fat way of eating that’s gaining popularity. Did you know that the ketogenic diet was commonly prescribed for people with diabetes before insulin became available in 1921? Although Keto diet has been around for a long time, there is new science behind this latest diet trend. Let’s take a look and translate the evidence to credible information you can use.

Keto Basics

Our bodies’ preferred fuel for energy is carbohydrate (also called carbs). When carbohydrate is scarce in the diet our bodies switch to an alternative fuel source which could be either fat or protein. This fuel switch is an adaptation that helped humans survive periods of famine.

Using fat as the alternative energy source produces compounds called ketones which are the by-product of fat breakdown for energy. When there is not enough carbohydrate available to meet the body’s energy needs ketone levels rise in the blood and ketosis occurs. Ketosis can come about either by fasting or by strictly limiting carbohydrate intake.

The Keto Diet

The keto diet is a way of eating that mimics the effects of fasting. The real ketogenic diet is not just any ‘low carb’ diet. It is a very low carbohydrate diet that is also very high in fat compared to the way most people eat. The keto diet approach is so low in carbohydrate that it forces the body to switch its fuel source. This big change in the types of foods eaten causes the body to go into ketosis, which means its burning fat for fuel instead of the carbohydrates.

There are many versions of a keto diet and typical ketogenic diet is about 20-50 g/day net carbohydrate (carbohydrate minus fibre). This translates to 5-10% of energy from carbohydrate.1 At the same time, fat is increased to about 70% to 80% of total calories, and protein intake is moderate. The chart below compares the proportion of calories from fat, protein and carbohydrates of the typical keto diet to a typical Canadian diet.

The keto diet adjustment period and maintenance can be challenging as the body changes over to a very low carbohydrate fuel environment. Dietitians find it can take about a month to get into the routine of a true ketogenic diet.

Comparison of Energy Source in Keto Diet and Dietary Recommendations

Typical Keto dietDietary Reference Intake
% EnergyIn a 2000 cal/day diet% EnergyIn a 2000 cal/day diet
Fat65 - 80%144 g - 178 g / day20-35 %44 -78 g / day
Saturated FatLess than 10%< 22 g/ day
Protein20 - 25%100g - 125 g / day10-35 %50 - 175 / day
Carbs 5 - 10 %
(net*)
25g - 50 g /day45-65 %225 - 325 g / day
*Net = sugars + starch (NOT fibre)All carbs: sugars, starch, fibre.

Nutritional Monitoring

To maintain a real keto diet and keep the body in ketosis, a person’s eating plan needs to be well thought out. Remember it’s all about really limiting carbohydrates and increasing fat without eating too much protein. This challenging approach is needed to restrict the body’s use of carbs and glucose production and force it into ketosis. Most people find it hard to stay on a true ketogenic diet, and if you’re trying to follow the keto diet, it’s a good idea to check in with your licenced health care professional such as a medical doctor or registered dietitian who can monitor your ketone levels, energy levels and cognitive function.¹

Many people do a ‘modified keto’ diet which is different from the true ketogenic diet described above. The switch over to burning fat as the preferred body fuel and the production of ketones may not be the same depending on the diet compositions. In general, most people do try to eat less carbs, and especially less added sugars.

Bottom Line

The foundation of the keto diet is very low carbohydrate intake with a high fat and moderate protein intake in comparison to the way most people eat. A well formulated ketogenic diet forces the body to shift from burning carbohydrates for energy to using fat instead. Modern science is emerging on the extreme restriction of carbohydrates in the keto diet and for people following a true ketogenic diet, a health care professional’s guidance is recommended. Dietary guidance for the general population includes reducing added sugars and including whole grains and pulses.

 

1 Dennett, C. (2019) The ketogenic diet for weight loss- How wide is the divide between the hype and research. Today’s Dietitian.