Research into Calorie Restriction (CR)
CR diets have been used in laboratory studies to look at the effects of reducing calorie intake on health and longevity. In 1935, a study showed that rats who were put on a restricted - but nutritionally complete - diet attained ‘extreme ages’ beyond those of normally fed rats.
Another study in mice in 1986 found that for every degree of CR there was an associated increase in longevity. In other words, the greater the restriction of their diet the longer the mice lived. The mice with the most restricted calorie intake lived half as long again as normal mice, reaching an average age of 53 months - the longest ever recorded lifespan of mice.
In humans, studies into the impact of CR on our own lifespan are showing signs that CR can lead to beneficial changes to signs that predict serious diseases like cardiovascular disease and diabetes. These signs - known as biomarkers - show changes that include lower total cholesterol, lower levels of fats in the blood, lower blood pressure and improved blood sugar regulation.
Improved Brain Function through Calorie Restriction
Other studies have looked at the impact of CR on our brain function as obesity has been linked to a higher risk of dementia and rapid cognitive decline in the elderly. Obesity in young adults has been linked to a lower density of grey matter in certain areas of the brain. CR has also been shown to increase the growth of new neural pathways and learning in mice and reduce signs of brain-aging in primates.
It is important to note that all of these studies of calorie restriction included a diet of complete nutrition i.e. only the amount of calories were reduced not the nutritional content.
The clear conclusion here is that we can be healthier if we eat smaller amounts, but these must be smaller amounts of highly nutritious food.
Obvious exceptions are in the sick and the elderly. When we are sick or elderly we may lose our appetite and become undernourished. These are times when we should really pay attention to eating more calories to recover or sustain our health.
This final point brings me to the topic of appetite. When I ask patients how their appetite is, the usual reply is ‘TOO GOOD!’ with a big sigh. This implies people are eating too much or too often. A healthy appetite means one where we sit down to eat genuinely hungry at set or regular meal times. Sitting down with an appetite means we will enjoy and savour our food.
If we graze through the day through stress, boredom or cravings we can end up ruining our natural appetite and enjoy our meals less.
Chinese wisdom on appetite says that we should arrive at the table hungry, and leave a little hungry too. Stick to the advice of stopping eating when 70% full. You’ll never have to count calories again and you might live longer to enjoy many more meals in the future.
Next week: How to Eat Part 2 - Regular Eating