Until not so long ago, nutrition experts advised eating small and frequent meals throughout the day.
Today, the view is changing and the practice of intermittent fasting (IF) is fast emerging as a way of eating − it is not a diet − which involves periodic short fasts ranging from 14 to 48 hours that can produce substantial health benefits. IF is as simple as extending the window between dinner and the first meal of the next day.
There are no restrictions on the amount of food one consumes during the eating window, although choosing a whole food, mainly plant-based, diet that is high in fibre intake from a variety of plants, fermented foods such as yoghurt, kefir, kimchi and kampuchea (to improve the diversity of microbiome of the gut) with plenty of protein (mainly from lentils, beans, legumes) and healthy fats, and maintaining good hydration, are essential. No sugar and reduced refined carbohydrates like flour are included.
IF emphasises food timing rather than denial of foods. It is an approachable health and weight-loss strategy.
How IF works
The benefits of IF is through regulation of the hormone insulin. The main function of insulin is to regulate the glucose (sugar) level in the blood. It promotes the lowering of blood glucose by facilitating the storage of glucose (calories) into the liver, pancreas and fat cells.
Chronically high levels of insulin is associated with diabetes, obesity, liver disease, cardiovascular disease, metabolic disease, cancer and cognitive decline.
There are different approaches to intermittent fasting but time-restricted eating seems to be the most popular method as one sleeps during part of the fast.
One only eats during a specific window of time which might be most convenient and best suited to the individual. This could start with 12 hours of fast and increased to 14, 16 and 18 hours as tolerated by the individual. It is important to keep oneself hydrated with fluids, mainly with water, but coffees and teas can be included.
IF can be done a few days a week or even daily as one gets used to it.
During the eating window, one does not need to restrict on calories as long as the calories are from healthy whole foods, low in refined carbohydrates and high in phytonutrients, with plenty of healthy fats and protein.
Try to avoid eating late in the evening.
When practised consistently, time-restricted eating, even for two or three days each week, appears to produce powerful results.
Benefits of IF
The following are some of the benefits of intermittent fasting.
Digestive system: Total transit time for food in the body averages 53 hours. To eliminate waste, the digestive system deploys the migrating motor complex (MMC) which propels it towards the exit.
MMC is more active between meals. It reverses signs of inflammatory bowel disease, encourages gut tissue regeneration and promotes the growth of beneficial gut bacteria (microbiome).
Weight loss: IF facilitates weight loss through insulin production. As the insulin level decreases, fat burning improves.
Insulin is the main storage hormone for fat. When we eat, insulin goes up and we store fat or glycogen in the liver. When insulin decreases, we start to break down glycogen and fat.
Low levels of insulin tell the body to start burning its stored fat.
Intermittent fasting emphasises food timing rather than denial of foods
It is important not to restrict calories during the eating window but to include quality food in the calories consumed.
Restricting calories on a chronic basis lowers the metabolism as the body thinks it is starving and goes into fat-storing mode − one reason why reduced-calories diet usually fail eventually.
Type 2 diabetes: Type 2 diabetes and pre-diabetes are characterised by blood sugar imbalance and chronically high insulin.
IF, with an eating window early in the day, improves insulin sensitivity and even reversal of diabetes.
This needs to be done under medical guidance.
Cardiovascular health: IF has been linked to lower levels of LDL (so-called bad cholesterol) and weight loss that play a role in cardiovascular health.
Atherosclerosis is a chronic inflammatory condition in which plaque accumulates in arteries – the leading cause of vascular disease.
IF has been shown to lower the level of inflammation by lowering levels of insulin and sugar.
Cognitive health: Abnormal glucose is responsible for 60 per cent of cognitive decline (dementia).
By helping to regulate and keep blood sugar under control, IF is a lifestyle that can have long-term benefits on brain health.
IF also increases production of brain-derived neurotrophic factor (BDNF) which helps boost resistance to cognitive degeneration.
Cancer: IF is a promising nutritional approach for cancer prevention as it protects against many of the risk factors such as obesity, type 2 diabetes and inflammation.
Fasting during chemotherapy has also been shown to reduce the side effects of treatment while increasing efficiency.
There is research on not eating for 13 hours overnight for cancer prevention and also delay in progression of a range of cancers.
Periods without food help build the immune system which is so important in pandemic times.
Ageing: IF has been shown to slow down ageing by protecting and promoting the lengths of chromosomes (telomeres) which enable the cells to live longer and be healthier, and also by promoting autophagy which is a process in which the body breaks down and discards non-functioning cell components.
Telomeres are also damaged by cigarette smoking, stress and poor diet which affect the microbiome of the gut.
Shorter telomeres are associated with accelerated ageing and cancer.
IF is not for everyone
There are groups of people who should avoid intermittent fasting and these are:
▪ Pregnant and breastfeeding women;
▪ Children;
▪ Anyone with a history of eating disorders;
▪ Underweight individuals, especially those who have a BMI under 20.
It is also strongly advisable to be under the guidance of a professional, especially those who are diabetic.
Pankaj Pandya is a general practitioner with special interest in lifestyle medicine and a member of the British Society of Lifestyle Medicine.