Unraveling the 5:2 diet
An interview with professor Kerstin Brismar
by Kim Franson
Have you heard of the 5:2 diet? You’d probably answer “yes”, right? The 5:2 diet is the latest and most popular method of losing weight and has been the talk of the town for about two years now. Eat just five hundred kcal per day for two days a week and whatever you like during the remaining five weekdays! The claims are that you will look slim and healthy, be more alert at work, live longer, just to name a few. It may seem like a no-brainer. But as is often the case with diet fads, there is a huge discrepancy between the claims proponents make and what the science actually say. Skeptics claim there is little evidence to conclude that the 5:2 diet really works as advertised but maybe that’s about to change? The research of the renowned professor Kerstin Brismar at the Karolinska Institute aims to prevent diabetes and its complications. “A healthy diet is a critical part of preventing diabetes, and we’ve been doing studies on different types of diet recommendations during the last five years”, Brismar says. I recently had the honor of chatting with Brismar to hopefully straighten out a thing or two.
“It was a wild era, full of philosophical and political discussion in which I was often engaged until 4 in the mornings”
“I was a medical student here ‘round 1968 – It was a wild era, full of philosophical and political discussion in which I was often engaged until 4 in the mornings”, replies scientist Kerstin Brismar when asked about how she first got involved with the Karolinska Institute. A scarf worn around professor Brismar’s head sort of like a bandana gives a hip feel to this otherwise normal looking 68-year-old – and as soon as she starts talking about the early years, her exhilarated face and eyes give me a flash of how “wild” she indeed must have looked as a young determined medical student about fifty years ago. As we sit down in the office by her lab right next to New Karolinska Solna, I learn that the young Miss Kerstin was engaged in several of the societies and committees of Medicinska Föreningen. “We ran our own restaurant back then, of which I was chairman, as well as being caretaker of “Solvik”, the sports cabin of Medicinska Föreningen.”
“As I’ve been involved in research here ever since medical school, I never really left the Karolinska Institute,” says Brismar, who first specialized in gynecology and then endocrinology. She advanced from one position to another and finally became professor in 1998, a position that she still holds. However, due to the harsh policy of Sofia-hemmet, of not allowing anyone over sixty-seven years of age to continue their clinical work, Brismar was recently shut off for being “too old”. “Though, the flipside of it all is that I have all the more time to do science now”, cheers Brismar, “After all, I have a huge lab and numerous PhD’s to attend to”.
“As of today, we frankly don’t know what people should eat, or not eat, to stay healthy” As the National Board of Health and Welfare has traditionally told us to eat lots of carbohydrates and only low quantities of fat, Professor Brismar wanted to investigate how these recommendations affect our bodies. She goes on saying: “I wanted to compare the conventional high carb low fat diet with a bunch of other diets such as high fat low carb-, high dietary fiber- and high protein diets.” The subjects in the studies were given the different diets in the quite cozy restaurant right next to Brismar’s lab rather than inside the actual lab itself. Tests were preformed before and after to see how the meals would affect blood sugar, blood fats, inflammation and oxidative stress, all of which are important markers for cardiovascular disease. “We want to know how our demand for insulin is affected by what we eat and contrary to what one might think, there actually aren’t that many studies performed yet that specifically examines this topic.” When the study is completed, hopefully before the end of the year, Brismar and her team hope that their results can be used to give better advice to people about what diet is most healthy. “As of today, we frankly don’t know what people should eat, or not eat, to stay healthy”.
In another study of Brismar’s, the subjects ate “neo-nordic food”. “By neo-nordic food”, explains Brismar, “we mean a special Nordic version of the well-known Mediterranean diet, appreciated around the world for its prophylactic properties regarding cardiovascular disease.” So instead of the Mediterranean fruit, common Nordic fruits such as apples, pears, raspberries and blueberries were used. Likewise, as far as vegetables and root-crops were concerned – only the common Nordic varieties made it on the menu. Moreover, they used canola-oil instead of olive oil – hazelnut instead of almond and so on. The study showed, quite conclusively that “Neo-Nordic food”, just like its Mediterranean counterpart, protects against diabetes, cardiovascular disease and cancer.
Since Brismar’s area of expertise includes insulin-like growth factors, IGFs, she was called in to be the expert commentator on Swedish national TV when science journalist Michael Mosley’s BBC-documentary was shown last year. “The documentary about the ‘5:2 diet’ really caught my attention and I wanted to take a closer scientific look at this new method”, Kerstin Brismar says. “Up until now, only a handful studies on the 5:2 diet have been published.”
“Try buying just one hotdog today and the vendor would assume you’re buying it for a child and not an adult”
Kerstin goes on to explain that we generally eat too much these days – caloric intake has increased a lot since the eighties among children as well as adults. Whereas the average caloric intake in the USA was about 1800 kcal per day in the eighties – the corresponding value today is about 2400 kcal. That’s a huge increase. We also don’t do as much exercise now as we did then. “Look at today’s meal-sizes”, says professor Brismar, “everything’s larger, larger drinks, larger burgers, larger plates. Try buying just one hotdog today and the vendor would assume you’re buying it for a child and not an adult – that wasn’t the case thirty years ago.”
“It’s a zero-sum game – what we put in, we must use, or our body will store it as fat.” This great change in eating behavior, explains Brismar, makes us put on a lot of extra weight, especially when we become middle-aged – but even kids become overweight nowadays. “It’s a zero-sum game – what we put in, we must use, or our body will store it as fat.” Although this equation may seem simple, it’s not that easy for people to wrap their heads around it in their everyday lives. For example, research has shown that labeling meals with their corresponding calorie-content has little to no effect on what meals people choose in restaurants. Perhaps we should instead be enlightening people on how much they’d have to exercise to burn those very calories.
“However”, says Kerstin, “I wanted to know how this 5:2 diet would work on different groups of people – who would follow through and who wouldn’t.” She also wanted to know what the typical personality traits were in those who could stick to the diet, if there are differences between men and women, differences between diabetics and non-diabetics etc. Brismar goes on to explain that we must have the answer to these questions to be able to give advice to people. And so, she started the 5:2 diet study in December last year. Says Brismar: “We will have a total of one hundred participants in this study – at present there are sixty subjects, ten new ones each month”. So far, the results look very promising according to Kerstin.
“The 5:2 diet appears to be the easiest diet for people to stick to over time, and that’s a huge plus.”
It seems like the 5:2 diet is an easy enough protocol to stick to. Whereas many people find it very hard to eat just 1700 kcal per day, every day, (which is a normal weight loss protocol) eating 500 kcal per day, 2 days a week is more convenient. “The data suggests that it doesn’t really matter how you decrease your overall caloric intake, the positive effects on the body’s biochemistry are still the same. You get increased insulin sensitivity, less abdominal obesity, decreased inflammation, better IGF-values, etc. However, the 5:2 diet appears to be the easiest diet for people to stick to over time, and that’s a huge plus.” Aside from a lower overall caloric intake, there may also be other upsides to the 5:2 intermittent fasting diet – it could have a positive effect on our cells’ ability to repair themselves. The implication of which would be that intermittent fasting, as in the 5:2 diet, would reduce the risk for somatic mutations to propagate, hence lower the risk of developing cancer. “It is not yet clear if this works in humans”, Kerstin Brismar says, “but that will indeed be the topic for my next study.”