Older adults who go long stretches between meals may be speeding up the accumulation of chronic diseases, according to a new Swedish study that challenges the popular image of fasting as a universal health booster. Researchers at Karolinska Institutet in Stockholm found the connection was strongest among people aged 78 and above, a group that has been largely left out of fasting research.
The study, published in the Journal of Internal Medicine, drew on data from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K), tracking 2,981 participants aged 60 or older at the start of the period. Over a 15-year follow-up, those who waited 14–24 hours between meals saw chronic conditions pile up noticeably faster than those who kept intervals of 6–11.5 hours.
The team noted the link held for cardiovascular and neuropsychiatric diseases, but not for musculoskeletal ones. They also stressed that the observational design can’t prove cause and effect — only that the two track together.
“Much of the research on fasting has been conducted in younger or middle-aged populations. Our findings suggest that the associations may be different in older adults, particularly among the oldest age groups,” says study last author Adrián Carballo Casla, a postdoctoral researcher at the Aging Research Center at Karolinska Institutet.
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Most current science on fasting leans heavily on younger bodies, which metabolically behave in ways that older ones simply don’t. The authors point to nutritional and physiological challenges that come with age, meaning that what works at 35 may not translate at 80. There may also be meaningful differences between the lower and upper ends of the older population itself.
They cite earlier observational work in community-dwelling older adults showing that longer habitual fasting times are tied to adverse metabolic biomarkers and poorer lower extremity function. That is a separate line of evidence, but it points in the same direction.
Intermittent fasting has ridden a wave of popularity, pushed heavily by social media personalities promising quick metabolic fixes. The scientific record has been inconsistent. A study published earlier this year suggested that intermittent fasting is unlikely to produce weight loss in obese and overweight adults, compared with traditional dietary advice or no changes at all — a finding that drew disagreement from multiple experts.
One author of that study conceded that intermittent fasting might be a reasonable weight loss option for some people, but cautioned that the current evidence “doesn’t justify the enthusiasm” surrounding the habit online.
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Other research has found potential upsides. A separate study linked intermittent fasting to benefits for polycystic ovary syndrome — now renamed polyendocrine metabolic syndrome — as weight loss lowered testosterone levels in affected women. A separate small-scale pilot study proposed that intermittent fasting may reduce dementia risk by
The Swedish team’s findings don’t erase those possibilities, but they complicate the picture. Fasting may carry different trade-offs depending on age, health status, and what exactly a person is hoping to achieve. The authors note that robust evidence in humans remains thin overall, and that excessive fasting may carry health risks that warrant caution in older adults.
For the oldest groups, the new data suggests that long meal intervals might not be the harmless habit some make it out to be. The researchers say the next step is figuring out why the association appears so clearly in the oldest participants — and whether shorter eating windows, or different meal timing patterns, might alter the outcome.
