23rd May 2016
Eat Fat, Cut the Carbs and Avoid Snacking to reverse obesity and type 2 diabetes
A report released today by the National Obesity Forum suggests that current dietary guidelines are wrong and advises a diet high in fat (including saturated fat) and low in carbohydrate for prevention of heart disease and type 2 diabetes. The ideas put forward in this opinion piece are contrary to the advice of health organisations around the world. Suggesting that a healthy diet should be high in fat, with no consideration of calories, is not based on sound science and is detrimental to the work going on to combat our obesity crisis and tackle risk of chronic diseases such as cardiovascular disease.
Although differences of opinion are inevitable in any field of science, this report presents views that are not widely held by the scientific community. Whilst knowledge of the link between diet and health continues to evolve, there is a substantial evidence base supporting dietary patterns that are at odds with the perspective from NOF. Recent, in-depth reviews of the scientific literature, including by the Scientific Advisory Committee on Nutrition in the UK and the Dietary Guidelines Advisory Committee in the US, have resulted in advice to consume a diet that contains plenty of fruit and vegetables, moderate amounts of fat (replacing saturated with unsaturated fats whenever possible), with meals based on starchy foods (predominantly wholegrain or high fibre versions), and limited amounts of free sugars.
The causes of obesity are complex and the type of diet that is best for losing weight has been widely debated for many years. However, balancing energy (calorie) intake with energy expenditure is the fundamental determinant of weight maintenance. The success or failure of specific weight loss diets depends on how well people adhere to them and this goes beyond their nutrient composition (e.g. proportion of fat and carbohydrate) to issues of palatability, convenience, satiety and personal beliefs.
Evidence for the impact of saturated fatty acids on raising cholesterol is available from a number of studies which have shown that their replacement with unsaturated fatty acids or complex carbohydrates reduces low-density lipoprotein (LDL or ‘bad’) cholesterol, and there is strong evidence high LDL-cholesterol levels are associated with increased risk of heart disease. However, the relationship between saturated fat and heart health is more complex than the simple message of ‘saturated fats are bad’. Firstly, not all individual saturated fatty acids have the same effect on blood cholesterol and secondly, reducing saturated fat in the diet without due attention to what replaces it may not have a positive impact on cardiovascular disease. This latter point has not been appreciated in much of the press coverage relating to this issue recently. Also, not all foods containing a higher proportion of saturated fatty acids will have the same effect on health because of the presence of other health-promoting constituents within the particular food.
Whilst opinion pieces may be of interest they should not be given the same credibility as peer reviewed, systematic reviews. Doing so will result in widespread confusion when there is a need for consistent information about healthy eating and physical activity to encourage habits that can make a difference to the health of the nation.