A BBC Horizon programme presented by Michael Mosley. This programme explored the role of diet and nutrition in ageing.
At Cornell University researchers are studying a genetically modified mouse strain, which exhibits longevity (longer life) with a calorie restricting diet. This work has been extended to human study at Fontana Washington University. Here, they have set up a long-term study of dietary intervention. The principal investigator was quite confident that the people undertaking this approach are a new species. I doubt this very much. Participants are restricted to 1,900 calories a day, usually eaten at breakfast as a huge bowl of fruit. Time will tell if this approach does indeed lead to a longer life, but if positive results were needed, age-related tests were conducted. These included assessment of balance and reaction times, as well as blood tests for metabolic markers, and levels of body fat. Mr Mosley’s assessment was pronounced as ‘not good for his age’, but the balance and reaction time tests are both subjective and can be improved with practice. More alarming was the absolute declaration that following the calorie restriction programme for just one year will result in a reversal of disease progression. In fact, the researcher went on to say that after following the diet for 10 years, J (a volunteer) would never develop a stroke or heart attack.
The truth is that in order to fully assess the risk of death from cardiovascular disease or cancer, we would need to sequence every bit of DNA in every person in the world, follow those people from birth to death, and analyse their lifestyles for diet, exercise and environmental factors. Then, we might be able to say who will die from heart attack, or not. Some research, including my own, has identified important genes, which contribute to the risk. I have also found out that the normal variation of these genes, interacting with certain environmental factors, like stress, injury or infection, can affect the way the body responds. So, you see, it is a very complex picture, and not simply down to calorie restriction.
Professor Valter Longo, from the University of Southern California does add some science to the discussion. His research centres around an important metabolic protein, Insulin-like Growth Factor 1 (IGF1). Reduced levels of IGF1 in the blood have been associated with slowing cellular metabolism (the so called ‘go,go’ mode), increased repair of DNA damage and protection from age-related illness, in a genetically modified laboratory mouse strain.
Ex vivo research (that is, in cells taken from the animal’s body) have shown that cells in ‘go’ mode are more susceptible to cancer, as they do not show efficient cellular repair. Studies in humans have shown that calorie restriction together with a low protein diet leads to reduced circulating IGF1 levels in the blood. The mechanism of action for this is that as glucose (blood sugar) is depleted in the body, the body (in particular the large muscles) start burning fat for fuel. The liver stops or slows production of IGF1, pushing the cells into repair mode. This is not a happy state of affairs for the body of an active man or woman. Prolonged fasting can be dangerous and should only be done under medical guidance. Extreme metabolic changes can occur with short fasting protocols too. Proponents of the alternate day fast or the 5-2 fast regimes often report that they are unable to exercise on fast days due to dizziness and weakness.
The main tenet of the piece is portion control, which I endorse. It’s no secret that if you eat less and move more, your body will be stronger and healthier, provided of course that you maintain adequate nutrition. And the emergence of these fasting diets for sustained weight loss should be viewed with some skepticism.
There was no discussion about the role of our genetic make-up and ageing, or longevity. Yet, many of us will know people who live long and when asked the secret, simply say eat well, exercise a bit, and have fun. Sounds good to me.