A new study of older adults has found that people who routinely went longer without eating accumulated chronic diseases more quickly over time, challenging the popular idea that extended daily fasting is broadly beneficial regardless of age. The research, conducted by scientists at Karolinska Institutet and published in the Journal of Internal Medicine, examined habitual meal timing in nearly 3,000 adults living in Stockholm. The association was especially strong among participants aged 78 and older, the age group in which nutritional vulnerability, frailty and multiple diseases are often most pronounced. The findings do not prove that fasting causes illness, but they raise important questions about whether meal-timing strategies promoted to younger adults can be safely applied to the oldest members of the population.
The study drew on data from the Swedish National Study on Aging and Care in Kungsholmen, known as SNAC-K. Researchers included 2,981 people who were at least 60 years old when they entered the study and followed them for as long as 15 years. To estimate eating patterns, participants reported when they typically consumed food during a 24-hour period. From this information, investigators calculated the longest interval between meals on a usual day. This measure was intended to capture habitual fasting duration rather than a short-term dietary experiment. Participants were then assessed over time for the emergence or accumulation of chronic conditions, allowing the researchers to examine whether daily meal spacing was linked to the progression of multimorbidity, the medical term for living with several chronic diseases.
The clearest contrast emerged between participants whose longest daily interval without food lasted six to 11.5 hours and those whose longest interval extended from 14 to 24 hours. Older adults in the longer-interval group accumulated chronic diseases at a faster rate. The pattern was observed when researchers considered the overall number of chronic conditions and remained apparent for cardiovascular and neuropsychiatric diseases. Cardiovascular conditions include illnesses affecting the heart and blood vessels, while neuropsychiatric disorders involve the interaction of neurological and mental health processes. The researchers did not observe the same association for musculoskeletal diseases, suggesting that meal timing may not relate equally to every category of illness.
The results are significant because fasting research has largely focused on younger and middle-aged adults, many of whom are studying fasting as a strategy for weight control, metabolic health or longevity. In those populations, time-restricted eating and intermittent fasting have produced mixed results, with some studies reporting modest improvements in body weight, blood glucose regulation or insulin sensitivity. Older adults, however, face a different biological and clinical landscape. Aging is accompanied by changes in appetite, digestion, muscle mass, kidney function and the body’s ability to respond to nutritional stress. A long interval without food may therefore have different consequences in later life, particularly for people who already eat small quantities or have difficulty maintaining weight.
One possible explanation is that prolonged gaps between meals could make it harder for older adults to consume enough energy and protein across the day. Adequate protein distribution is important for maintaining skeletal muscle, and insufficient intake can contribute to sarcopenia, the age-related loss of muscle mass and strength. Extended fasting could also affect blood glucose stability, especially in people taking medications for diabetes or other metabolic conditions. If long meal intervals are accompanied by inadequate hydration, reduced appetite or episodes of overeating later in the day, the overall pattern may become nutritionally unbalanced. These mechanisms remain hypotheses rather than conclusions from the study, but they illustrate why the effects of meal timing may depend on age, health status, medication use and total dietary intake.
The association was strongest among adults aged 78 and older. This finding may reflect the greater physiological sensitivity of the oldest participants, who are more likely to experience frailty, unintended weight loss, impaired appetite and multiple medications. It may also indicate that the same fasting duration represents a greater nutritional challenge for someone with low energy requirements but reduced ability to eat large meals. In advanced age, a missed meal can account for a substantial share of the day’s calories and protein. At the same time, the study cannot determine whether long fasting intervals directly accelerated disease accumulation or whether existing health problems caused people to eat less frequently.
That distinction is central to interpreting the findings. The research was observational, meaning that investigators measured naturally occurring eating habits rather than assigning participants to fasting schedules. People who had longer intervals between meals may have differed from those with shorter intervals in many other ways. They could have had poorer appetite, more severe disease, lower mobility, different sleep patterns or socioeconomic circumstances that affected both eating behavior and health. Some participants may also have lengthened their fasting periods because illness made eating difficult. This phenomenon, known as reverse causation, could make fasting appear to predict disease progression when underlying disease was actually influencing meal timing. Although statistical analyses can account for some factors, they cannot eliminate every source of bias in an observational study.
The researchers also relied on participants’ recollection of when they typically ate, rather than continuous measurements from food diaries, digital devices or controlled feeding studies. Self-reported information may not capture irregular meals, snacks, drinks containing calories or changes in eating patterns over the 15-year follow-up period. The longest daily interval was estimated from a reported routine, so it should not be interpreted as a precise measurement of every fasting episode. Even with these limitations, the long follow-up and detailed health data from SNAC-K provide a valuable view of how habitual meal timing may relate to aging and multimorbidity in a real-world population.
Adrián Carballo Casla, the study’s last author and a postdoctoral researcher at Karolinska Institutet’s Aging Research Center, said the findings suggest that fasting may have different associations in older adults, particularly among the oldest age groups. The message is not that every older person should eat more frequently or that fasting is inherently dangerous. Instead, the study points to the importance of individualized nutritional advice. For an older adult who is healthy, maintains body weight and consumes sufficient nutrients, a particular eating schedule may be well tolerated. For someone experiencing frailty, diabetes, unintentional weight loss or multiple chronic conditions, long gaps between meals may require closer medical and dietary supervision.
The study adds a timely caution to the rapidly expanding conversation around intermittent fasting and longevity. Meal timing is only one part of nutrition, and the quality, quantity and distribution of food may be more important than the fasting window alone. Future research will need to test specific eating schedules in randomized clinical trials involving older adults and measure outcomes such as muscle strength, nutritional status, blood glucose, cardiovascular health and cognitive function. Until those studies are available, the new evidence supports a careful approach: fasting strategies developed for younger populations should not automatically be assumed to benefit people in later life, especially those aged 78 and above or those already living with several chronic diseases.
Subject of Research: People, particularly older adults aged 60 years and older
Article Title: “Habitual fasting duration and accelerated multimorbidity in older adults”
News Publication Date: 20-Aug-2026
Web References: https://doi.org/10.1111/joim.70150
References: Luis Kalmbach, David Abbad-Gomez, Giorgi Beridze, Fernando Rodríguez-Artalejo, Davide Liborio Vetrano, Amaia Calderón-Larrañaga and Adrián Carballo-Casla, “Habitual fasting duration and accelerated multimorbidity in older adults,” Journal of Internal Medicine, published online August 20, 2026. DOI: 10.1111/joim.70150
Image Credits: Photo: Maria Yohuang. Image of Adrián Carballo Casla.
Keywords: older adults, fasting, meal timing, intermittent fasting, multimorbidity, chronic diseases, cardiovascular disease, neuropsychiatric disease, aging, nutrition, Karolinska Institutet, observational study
