The latest on low-carb versus low-fat

Years ago, I remember the 'low-carb' movement taking off. It was the era of the Atkins diet and word on the street was Jennifer Anniston was a big fan. For anyone who watched her as Rachael Green on 'Friends', she was the best possible advertisement for a low-carb lifestyle. Even Joey couldn't resist a cheeky, 'How you doin'?'.

Fast forward twenty years and debate still rages about diets. Although the selection on offer is longer than I could ever cover. The low-carb diet has not gone away though. It is still touted as one of the best diets for weight loss with proponents not only championing it's efficacy but also its ease of following. 

According to Sports Dietitians Australia, low-carb diets (depending on their exact make-up of macronutrients) can result in very rapid short term weight loss, but can leave you feeling nauseous, tired and constipated. Other medical studies have raised concerns about low-carb diets either due to the large amount of fats or proteins consumed in place of carbohydrate. A diet low in carbohydrate can impact on performance; carbohydrate is an important energy source for an active body and for our brains. 

The Journal of the American Medical Association (JAMA) is a powerhouse medical publication. So when their latest issue contained this article comparing low-fat versus low-carb diets, it's hard to ignore. This study aimed to look at the effect of either a low-fat or low-carbohydrate diet on weight loss but also on two other important variables.

Ever since I read Dr David Ludwig's book, Always Hungry, where he talks a lot about an individual's response to food and how that could impact on how that person deals with the food they eat and if they gain weight. This JAMA study looked at two variables for this: a participant genetics and how they made insulin when they were given food. 

In a nutshell, what they found was that people in both the low-fat and low-carb groups lost weight, around 5% of their body weight in each group over 12 months. They also had reductions in blood pressure, cholesterol and insulin. The rate of problems with the diet were low although a handful people wound up in hospital with issues that may have been related to the diet. The diets also did not show that someone's genetic makeup nor their insulin response was important for success in either diet.

The fact that both diets were successful may tell us that it's not a major issue where you get your nutrients from. However, there are a couple of issues here. First of all, both groups were given instructions on eating foods that were healthful, in addition to following their prescribed diet. This meant lots of vegetables and not much refined, processed food. This is good sensible advice for anyone to follow. 

Like a lot of studies when it comes to diet, this study gave people some guidelines to follow and then watched and waited to see what would happen. This can be tricky to get good answers from because we are not watching people 24/7 to see exactly how much they eat, if they're sticking to the diet or exactly how much activity they do. 

All in all though, it's interesting that there was no difference and honestly, when I read the scientific literature on diet, it seems to be the same thing over and over again. We seem to get more information all the time that shows that if there is an advantage, it's small. The two exceptions to that are the Mediterranean diet and the DASH diet, both of which seem to do consistently well in preventing disease, not just losing weight. 

While I'm not a dietitian, I think what we can take away with relative certainty from the dietary debate is that:

  • Avoiding highly processed, sugar laden foods is definitely useful
  • A diet high in fruit and vegetables, legumes and whole grains is a sound choice

The rest, I think, is still being worked out. 

For this round of low-carb versus low-fat, we still haven't got a winner. 

Don't forget, you can read more about your health in my new book, Can You Die of a Broken Heart? It's available now at all good bookstores, in store and online.