Is a very high fat, low carbohydrate diet good for you?

As the American Journal of Clinical Nutrition publishes an article highlighting the beneficial aspects of a high fat diet, is such an indulgent diet really good for you?sundayexpress

The article in question is:

Visceral adiposity and metabolic syndrome after very high-fat and low fat isocaloric diets: a randomized controlled trial.  It was performed by researchers at the University of Bergen in Norway.

So what did the study authors do? Well they recruited 46 men between the ages of 30-50, who responded to a advert in a local newspaper, they had to have a raised body mass index and waist circumference.  They needed to have no food allergies or regular medications and no severe disease diagnosis.

They were assigned to eat a specific diet for 12 weeks, either a very high fat, low carbohydrate diet, where they would get 73 percent of their energy from fat.  Or a low fat, high carbohydrate diet where 53 % of their energy would come from carbohydrates.

The participants were given a recipe book to help them with choosing meals that reflected their respective diet.  All particpants took a vitamin tablet and companies supplied some additional ingredients such as butter, coconut oil, a sugar substitute and plant based carbohydrate alternative.

Avoid hydrogenated fats, specific plant oils, sugar and highly processed foods

It’s worth noting that both diets emphasised low processed and low glycaemic food.  Both diets emphasised homemade meals.  Both groups were told to avoid hydrogenated vegetable fat, specific plant oils, sugar and highly processed foods.  They were also told to eat 500 grams of vegetables and fruits every day and to eat vegetables with every meal.  The high carbohydrate diet were also told to try and incorporate fruit juice.

2 men withdrew before the experiment started and a further 4 dropped out early on and 2 men were excluded because they hadn’t complied with the diet, leaving 38 in the final numbers, 18 eating the high carbohydrate diet and 20 in the very high fat diet.

Overall both diets led to the participants having smaller waists, less fat on their abdomen and a reduction in weight and overall there were less fats circulating in their bodies.  But we should take these results with a pinch of salt, firstly there really aren’t that many people in the trial, they’re also all men, all fairly young in age (30-50 years) and carrying no significant medical diagnoses.

The study is not really comparing like with like, to do that you would need a group of men eating their standard diet.  What we have here is men who were told to eat one of two diets which both promoted whole foods and emphasised an intake of fruit and vegetables.  Both diets used the same foods, but in varying quantities, so it can be argued that the benefits reflect eating whole foods over processed food.

The study ends with the following words, “Our study cautions against extrapolating short-term (1–2 mo) metabolic responses to longer-term effects of macronutrients on cardiometabolic risk.” i.e. just because we did this for 12 weeks, it doesn’t mean you will see benefits in the long term.