Low-fat diet is not the devil

The recent report  Eat fat, cut the carbs and avoid snacking to reverse obesity and type 2 diabetes by National Obesity Forum has stirred up a heated debate over fat consumption. It has been featured on the Guardian, Independent and The Telegraph. The main point of the report is: fat is not the devil, carbs are. It also advises on eating “real” food and avoid processed food.

Since the recommendations in the report are against the low-fat diet guidelines by US and UK, the headlines state the low-fat diet as “disastrous” or the NOF diet advice “extremely dangerous”. Some even claims that low-fat diet is the main cause of the obesity epidemic in the US by showing that obesity prevalence shot up after the low-fat diet published in the 1977. I wonder if these people serious believe what they are talking about or they just want to hit the headlines and become famous.

Let’s be rational. How many people actually follow the guidelines? Do the guidelines have any effect on people’s eating behavior? I will use the color wheels from What the world eats, that I wrote about in my previous post What the World Eats from 1961 to 2011 to illustrate this.


Here are two color wheels showing the US daily calories consumption in year 1976 and 1978, before and after the low-fat guidelines were published.

US 1976 1978

Do you see any difference? Do people follow the guidelines and eat less fat and more carbs? Not at all. Well maybe it takes some times to see the changes. So let’s look at the wheel for year 2011.

US 2011

Percentage of each type of food consumed is largely the same. There isn’t any significant increase in carbs or decrease in fat. What’s more, people are consuming 500 cal more every day in 2011. What does that means? Very obvious, people do not follow the diet guidelines. It is extremely difficult to change people’s diet. Even those diet interventions with long term intensive follow up and monitoring, hardly change people’s eating behavior. Every guideline advises to limit sugary drinks. How many people actually listen? If the guidelines can have such huge impact, so huge as to cause the obesity epidemic, the government doesn’t need to spend millions on diet interventions any more. If people do follow the diet advice, limiting their daily calories intake within the recommended range, there will not be so many obese people around the world. How can we term it as “disastrous” and blame it for causing obesity when it simply doesn’t have any impact on people’s diet? 

I agree that the low-fat diet has its limitations. But that’s the case with all kinds of diet advice. Diet advice cannot be perfect because the current available evidences are not able to tell us every single component of our diet is good or bad for our health. The reason being it is almost impossible to carry out randomized trials on a single diet component. Even for trials comparing two types of diets, low-fat vs high-fat for example, it is impossible to make sure people actually follow the assigned diet in the trial.

The main difference between the low-fat diet and NOF diet advice is on saturated fat. Low-fat diet recommends limited intake of saturated fat while NOF report argues saturated fat is not harmful. It is meaningless to argue who is right or wrong when the evidences are not strong enough to support either side. Meanwhile, let’s play safe and eat saturated fat at moderation.