Long fasting windows are often promoted as a metabolic shortcut. New research suggests the picture may change in later life, especially after age 78. But the finding is a warning signal, not proof that fasting causes disease.
Intermittent fasting is usually discussed as though age barely matters. A new 15-year study of older adults challenges that assumption.
Researchers followed 2,981 people in Stockholm who were at least 60 years old when the study began. Participants who routinely went 14 to 24 hours between eating occasions accumulated chronic diseases faster than those whose longest daily gap was 6 to 11.5 hours. The association was clearest among people aged 78 and older.
The result deserves attention. It does not justify panic or a claim that intermittent fasting is harmful.
What the researchers measured
The study used data from the Swedish National Study on Aging and Care in Kungsholmen, a long-running population study commonly known as SNAC-K.
Participants reported when they usually ate during a typical 24-hour period. Researchers defined habitual fasting duration as the longest interval between two eating occasions. They then tracked the accumulation of chronic conditions for as long as 15 years.
Longer fasting intervals were associated with faster growth in the total number of chronic diseases. The pattern also appeared separately for cardiovascular and neuropsychiatric conditions, but not for musculoskeletal disease.
Age changed the picture. The association was strongest in adults aged 78 and older, suggesting that a meal pattern tolerated earlier in life may carry different implications when appetite, muscle mass, medication use and recovery capacity begin to change.
What the study does not prove
This was an observational study, not a fasting trial. Researchers did not randomly assign people to different eating windows and then observe who developed disease.
That distinction is crucial because longer gaps between meals may be a symptom rather than a cause.
Older adults who are frail, unwell, socially isolated or experiencing appetite loss may eat less often. Disability can make shopping and cooking difficult. Depression, cognitive changes, medication effects and sleep disruption can all alter meal timing. Existing disease could therefore lengthen the fasting window while also making additional illness more likely.
The reported meal schedules were also self-reported. They describe habitual timing, not a carefully monitored time-restricted eating program with controlled calories and nutrient intake.
The study therefore cannot tell us whether intentionally shortening a fasting window would prevent disease, or whether a well-designed fasting routine would produce the same association.
Why age could matter
Fasting research has often focused on younger and middle-aged adults, particularly people with obesity or metabolic risk. Late life brings a different balance of priorities.
Maintaining muscle becomes increasingly important. So does consuming enough protein and energy, recovering from illness and coordinating food with medications. A long daily eating gap that reduces opportunities to meet those needs could be neutral for one person and harmful for another.
The new research does not establish that mechanism, but it makes the one-size-fits-all version of fasting advice harder to defend.
The evidence check
What we can say: Among nearly 3,000 older adults followed for up to 15 years, longer habitual gaps between meals were associated with faster accumulation of chronic disease. The relationship was most pronounced after age 78.
What we cannot say: The study does not show that intermittent fasting caused those diseases, that every older adult should avoid time-restricted eating or that changing meal timing will improve longevity.
What would strengthen the evidence: Randomized trials in older adults that measure dietary quality, calorie and protein intake, body composition, frailty, medication use and clinical outcomes, not just weight or short-term metabolic markers.
The practical takeaway
The finding should prompt more individualized questions, not a universal rule.
For an older adult who is weight-stable, well nourished and medically supervised, a defined eating window may be very different from unintentionally skipping meals because of illness or reduced appetite. For someone experiencing unplanned weight loss, weakness or difficulty eating enough, extending the fasting period could work against more urgent health goals.
Meal timing is only one part of the picture. In later life, the quality and adequacy of what happens inside the eating window may matter at least as much as the number of hours outside it.
Bottom line: Longer fasting windows were linked to faster disease accumulation in older adults, particularly after 78. That is a meaningful caution, but not a verdict against fasting.
Source
Kalmbach L, Abbad-Gomez D, Beridze G, et al. Habitual fasting duration and accelerated multimorbidity in older adults. Journal of Internal Medicine. Published online August 20, 2026.