Dr Michelle Harvie is an award-winning research dietitian funded by Prevent Breast Cancer. For the last 17 years she has specialised in optimum diet and exercise strategies for weight loss and preventing breast cancer and its recurrence. Her findings have been published in many major scientific journals. Dr Harvie is the author of the best-selling book The 2-Day Diet.
The recent headline ‘Food experts at war over new advice on nation’s diet’ highlighted opposing views on a healthy diet between leading doctors and scientists from Public Health England and the National Obesity Forum. Public Health England advise people to limit their intake of fat, especially saturated fat (found in fatty meat and high fat dairy foods), and to include carbohydrates (potatoes, bread, rice and pasta etc.) in all meals, which are also ideally wholegrain. The National Obesity Forum challenged this advice, suggesting dietary advice to promote low fat foods is potentially the biggest mistake in modern medical history. The experts who wrote this report suggest we should eat more fat including healthy fats such as nuts, olive oil and avocados. They state that saturated fat thought to be the ‘baddy’, may not actually be bad for your health when compared to a diet which is high in carbohydrates. They raise concern of the safety of certain vegetable oils like sunflower, corn, plus margarines, and highlight emerging evidence that saturated fat, including fat from dairy food, being beneficial for health.
These public disagreements understandably undermine public confidence, it is impossible to know who is right and what to believe. Studying the links between diet and health is complex, and not simply, is a food good or bad for us? Nutritional researchers like to argue the point for extreme changes in diet which is not very helpful for the scientific community, let alone the public who are left to make sense of it all.
Extreme diets which are very low in fat or carbohydrates are unlikely to be optimal, and they are certainly difficult to follow. Most research of extreme low carb or low fat diets ends up showing similar benefits as the participants end up on identical diets which are some way between the two extremes. So even if an extreme low carb or low fat diet was optimal, it would not work as people would struggle to stick to it. Taking an unhealthy food out of a diet will only make us healthier if we replace it with something healthy rather than another unhealthy food. Some studies have concluded saturated fat is not as harmful as thought as they have compared what happens when you replace this with sugar, which often has worse effects.
Should we have a low fat diet?
Have moderate amounts of fat. Fat is the most calorific food that we eat (9 calories per gram), so if you are watching your weight, you should not overdo fat in the diet. However, low fat diets don’t do much for health. One of the largest trials of low fat diets in the US (Women’s Health Study) included 48,835 US women and did not reduce weight or rates of cancer, heart disease and diabetes.
Should we limit saturated (animal) fat?
Yes. Saturated fats are linked to risk of heart disease and stroke, and some reports of it link it to cancer. Replacing saturated fat with monounsaturated fats has been shown to reduce the chances of heart disease or stroke, and there are some preliminary reports that it may help reduce risk of cancer. There is an emerging interest of whether saturated fats from dairy foods may be healthy, and not harmful like the fat in meat, but we need better evidence of this.
Should I have a low carbohydrate diet?
No. You don’t have to have carbs with every meal, but you do need some wholegrains in your diet such as cereals, bread, wholemeal pasta, brown rice and other grains to provide fibre.
The 2-Day Diet
We do not advocate an extreme low fat or low carb, or high saturated fat diet. The 2-Day Diet has two low carb days per week and five days of a healthy Mediterranean diet which has moderate amounts of healthy fats including nuts, olive oil, avocados, but limits saturated. It also includes moderate amounts of wholegrain carbohydrates, dairy foods, lean protein foods and fruit and vegetables.