On Monday 6th June I gave a short talk entitled 'A healthy balanced diet: evidence-based practice.' This was part of a day-long conference organized by Bucks New University on Ageing and Health - Intergenerational Perspectives. You can view the accompanying slides here
In preparing my talk, in which I sought to convince the audience that saturated fat is good for us and eating a lot of carbohydrate is bad for us, I again came across this remarkable story from my book, 'Twenty-First Century Nutrition and Family Health.' In 2002 doctors at Duke University, North Carolina, decided to conduct a study lasting 6 months to determine the medium-term effects of a low carbohydrate diet. This was an amazingly brave piece of research, because they allowed 41 overweight or obese volunteers to eat as much fat as they liked, so long as they restricted their carbohydrate intake to 25 grams a day! Actually the project started with 51 volunteers, but ten had to drop out for work or other reasons, including two who couldn’t keep off their doughnuts and bagels and pizzas. The remaining 41 volunteers, aged between 35 and 53, comprised both men and women, with the majority being white women. They all wanted to lose weight.
They attended regular meetings at which they were encouraged to take at least 20 minutes of aerobic exercise like walking, cycling or swimming three times a week. Blood samples were taken at these meetings. After they had lost 40% of whatever weight they were trying to lose they were allowed to increase their carbohydrate intake to 50 grams a day. That still isn’t much – one thick slice of bread! The rest of their diet consisted of unlimited amounts of meat, fish and seafood (e.g. beef, pork, chicken, turkey, fish, shellfish), unlimited eggs, 4 ounces of cheese per day, 2 cups of salad vegetables per day, and 1 cup of low-carbohydrate vegetables per day. The subjects were told to eat as much meat and eggs as they liked until their hunger was relieved. How about that for a weight-loss diet?
So what happened? On average the dieters lost 9kg in weight. Their LDL (considered an indicator of potential heart disease) decreased on average by 7%, a small improvement, and their cholesterol level fell by 5%. Their average HDL (considered a healthy indicator) increased by 19%, a substantial improvement, and finally their triglyceride level (a major warning sign for the development of heart disease) fell by an enormous 43%! The effect on their insulin levels was not reported.
Hence after 6 months’ eating unlimited amounts of fat and protein but strictly limited amounts of carbohydrate, the participants lost weight, lowered their LDL, cholesterol and triglyceride levels, and substantially improved their HDL. There were similar findings in an earlier independent study over a shorter period, but the improvements were even greater over the longer period of this study! All these changes were the complete opposite of what generally accepted wisdom would predict. But these are facts. The results demonstrate that either fat is good for us, or common levels of carbohydrates are bad for us, or both - at least if we take a certain amount of exercise regularly.
 Westman E C et al. Effect of 6-month adherence to a very low carbohydrate diet program. American Journal of Medicine, 2002; 113: 30-36.