How does the keto diet work and is it right for you?
September 15, 2020
The ketogenic or ‘keto’ diet has become a nutritional buzzword in recent years.
It’s a low-carbohydrate diet designed to switch the fuel your body uses from sugar to ketones - scientifically known as 'ketosis.' But what exactly does this mean? And is the keto diet right for you?
- What the keto diet is
- Whether the keto diet is superior to other approaches for weight loss
- The longer-term effects of restricting carbohydrates on your microbiome and your overall health
- How understanding your unique metabolism and personal nutritional responses is key to optimal health
What is the keto diet and how does it work?
There are several versions of the keto diet, but broadly speaking it’s a low-carbohydrate diet that restricts the number of vegetables, fruits, legumes (beans and pulses), grains, and refined sugars that you eat.
This means that your body doesn’t have easy access to its preferred fuel - the simple sugar glucose, which is produced when carbohydrates in your food are broken down.
Instead, your body takes stored fat and transforms it into chemicals called ketones, which it can use as fuel instead. When this happens, your body is said to be 'in ketosis'.
Supporters of the ketogenic diet say that it aids weight loss by increasing how much body fat you burn, increasing insulin sensitivity, reducing blood sugar fluctuations, curbing your appetite, and helping you feel full. But what does the science say? Let's take a look…
Are carbohydrates an essential part of our diet?
Promoters of ketogenic diets often argue that carbohydrates aren't an essential nutrient, and we can survive without them.
"The truth is carbohydrates are not an essential nutrient because our bodies can synthesize glucose through a biochemical pathway known as gluconeogenesis," says Kirstin.
But just because carbs aren’t ‘essential’, it doesn’t mean they aren’t good for us.
"You can argue that there is no minimum carb requirement, but that is ignoring your requirement for the micronutrients that are found in high-carb foods - like vitamins and minerals in fruit and vegetables - as well as fiber that feed your gut microbes," says Christopher. "So while technically, carbs are not essential, many carbohydrate-containing foods are an important part of a healthy diet."
Our PREDICT study shows that everyone responds to carbohydrates differently, and different types of carbs can affect each of us in different ways. For example, although rice and porridge are both carbohydrate-rich foods, one might trigger an unhealthy blood sugar response after eating while the other is just fine.
The important thing is to know how your body works and pick the right foods for you. Our at-home test kit lets you discover your unique responses to carbohydrates and fats, and provides personalized advice about the best food choices for your body to reduce dietary inflammation and improve your gut health.
Are low-carbohydrate diets like the keto diet better for weight loss?
Christopher was the lead researcher of the DIETFITS study, which compared high quality low-carb and low-fat diets for weight loss. In the study, over 600 people followed either a low-carb or low-fat diet for 12 months.
The result at the end of the experiment? There was no clear winner.
"There was an amazing amount of variability in results for both diets. Someone lost 30kg while someone else gained 10kg. That’s a 40kg or 80lb range of response to the same advice," says Christopher.
We still don’t know what makes one diet work for one person but not for another. However, the DIETFITS did show that genetics isn’t a good explanation for these differences - a finding that’s backed up by the results of our own research.
Does the keto diet improve blood sugar control?
Carbs make your blood sugar and insulin levels rise after you eat. This is all part of a healthy nutritional response, however, repeated, excessive peaks and dips in these biomarkers over time can overwhelm your body's normal, healthy responses and lead to dietary inflammation.
You might think that because of the lack of carbohydrates, people who have poor blood sugar control, or insulin resistance might do better on a low-carb or keto diet. But when the DIETFITS team took a closer look at their data, they found that this wasn’t true.
"The people who were most insulin resistant did not do better on low-carb than low-fat," says Christopher. These results contradict previous studies suggesting that people with problems controlling their blood sugar may do better on low-carb diets.
He explains that these earlier studies allowed people in the low-fat group to eat added sugar and refined grains, which are likely to cause poor blood sugar control.
"By focusing on getting our low-carb participants to eat a high-quality low-fat diet, with minimal sugar and refined grains, we diminished the difference that other people had found."
Christopher is currently running a study called Keto-Med, which is comparing the effectiveness of the keto diet and a Mediterranean diet for people with type 2 diabetes and prediabetes.
The Mediterranean diet restricts sugar and refined carbohydrates like keto but allows healthy, plant-based carbohydrates, including whole, unrefined grains, legumes, and fruit. People will follow both diets for three months, and then the researchers will compare their results in terms of weight loss and overall health.
"We're looking at if when you get rid of sugar and refined grains, there is then an additional benefit to getting rid of legumes, fruit, and whole intact grains. But I’m skeptical whether it will work," Christopher says.
So, should you go keto?
Beyond the potential food weight loss and blood sugar control, it’s essential to think about how a diet like keto might affect your overall health.
"Blood glucose is not the only thing that's important," says Christopher. "On a very low carbohydrate diet, you're not getting a lot of plant-based fiber that feeds the microbiome and helps fight off inflammation, and we don’t know the full health implications of that."
There are also potential health risks from eating a low carb high-fat diet like keto if it’s not right for you. Results from our PREDICT study show that unhealthy fat responses after eating are strongly linked with dietary inflammation, which may increase the risk of heart disease.
The take-home message? These extreme diets should not be your first choice for weight loss or improving your health.
"I think everybody should be starting with a foundational diet that involves eating more vegetables, more whole foods, less added sugar, and less refined grains," says Christopher "After that, there's a wealth of options based on your personal tastes and preferences."
Even after you have adopted this foundational, healthy diet, there's still lots of room for personalization.
In our PREDICT studies, we found that when different participants ate the same standardized tests meals, there was a huge amount of variation in their blood fat, glucose and insulin responses - even for identical twins. This tells us that individual responses to even the exact same foods can vary a lot, so it makes sense that we all need to eat differently to stay healthy and maintain our ideal weight.
Find out more:
- Ketogenic Diet – StatPearls
- A Ketogenic Diet to Lose Weight and Fight Disease – Healthline
- Effect of Low-Fat vs. Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial – JAMA
- Low-Carb and Ketogenic Diets in Type 1 and Type 2 Diabetes – Nutrients
- Is dietary carbohydrate essential for human nutrition? – The American Journal of Clinical Nutrition
- What happens when you eat carbs? – ZOE
- Should you try the keto diet? – Harvard Health