The effects of fasting from the age of 60 onwards

The issue has gained renewed attention following a study by the Karolinska Institute in Sweden, published this summer in the scientific journal Journal of Internal Medicine. After following nearly 3,000 people aged over 60 for 15 years, the researchers observed that those who regularly went without food for periods of between 14 and 24 hours developed chronic conditions more rapidly, an effect that was particularly evident from the age of 78 onwards. Although the data do not in themselves prove that fasting is the cause, nor do they allow us to establish a universal threshold, they do reinforce an important idea: going for prolonged periods without eating is not a neutral practice once a certain age is reached. What changes with age to make the body less able to tolerate this?

Francisco José Tarazona, a Doctor of Medicine and President of the Spanish Society of Geriatrics and Gerontology, points out that "as we age, our physiological reserves decline and we are more prone to nutritional deficiencies, loss of muscle mass and feelings of tiredness". Furthermore, many older people suffer from chronic conditions which “increase nutritional requirements or make it difficult to eat properly”, meaning that fasting can hinder the management of these conditions.

To take just one example, diabetes medication "could increase the risk of developing hypoglycaemia" if meals are skipped, according to Dr Samara Palma Milla, a member of the Spanish Society of Endocrinology and Nutrition. The specialist points out that "age, generally speaking, is associated with a higher likelihood of malnutrition and dehydration", and notes that there are medicines whose absorption or effectiveness changes depending on whether or not they are taken with food. Added to this is the fact that breaking one’s daily routine makes it easier to forget to take tablets, a factor that can affect treatment.

Rather than looking at the clock to work out how long it has been since you last ate, what really matters is the frequency and the person’s overall state of health. “Occasional fasting may have no impact, but when prolonged periods without food intake are repeated, particularly in frail individuals, the risk of functional and cognitive decline increases,” insists Tarazona. Nor are everyone’s needs identical. Two 80-year-olds may have different requirements depending on “the presence of illnesses, functional capacity and physical activity,” as Dr Palma points out.

One of the most sensitive issues concerns muscle, “which is essential for maintaining independence,” explains Tarazona, who links a continuous reduction in intake to the development of sarcopenia – that is, the gradual loss of this tissue which provides strength and functional capacity. What are the risks for older people? “An increased risk of falls and fractures, dependence on others for basic activities of daily living, heart or lung disease, cognitive decline, movement disorders and a poorer quality of life,” lists Palma.

And this is where a crucial difference lies: older people do not always fast by choice. They often start eating less due to a loss of appetite, the side effects of medication – such as nausea or a dry mouth – difficulties chewing or swallowing, or the sheer complexity of shopping for food and cooking when living alone. Tarazona sums it up with a very vivid phrase: "Sometimes, the problem isn’t that they don’t want to eat, but that eating has become an uncomfortable, difficult or even dangerous activity".

Families can spot certain signs before a more serious complication arises: “An increasingly empty fridge, food past its use-by date, less variety in the diet or a noticeable reduction in shopping,” says Tarazona. Paula Crespo, vice-president of the General Council of Official Associations of Dietitians and Nutritionists, adds that, when appetite is low, “rather than insisting on very large meals, it may be helpful to offer smaller portions throughout the day”. The aim, she points out, is to ensure “sufficient protein and energy intake”.

“A long period of fasting reduces the time available for eating,” Palma emphasises. For this reason, Crespo advises against having dinner too early or breakfast too late, whilst also warning about loss of appetite: “Loss of appetite is common among older people, but we mustn’t accept it as an inevitable part of ageing.” Tarazona, for his part, gets to the root of the problem: “We mustn’t just focus on how much they eat, but on why they’re eating less.”