Eating over a longer part of the day in adolescence linked to lower body weight in early adulthood, study finds

A new study has found that adolescents who eat over longer periods of the day – known as having a longer ‘eating window’ – may experience modest but measurable health benefits, both in their teenage years and into early adulthood.

The study, led by researchers at the Bristol BRC and using data from the Avon Longitudinal Study of Parents and Children (ALSPAC), is published in the journal Nutrients.

The research, which focused on dietary and health data collected at ages 7, 13, and 24, adds valuable insight into how time-limited eating, a popular dietary strategy in adults, may affect younger populations. While time-limited eating has been shown to improve body weight and metabolic health in adults, its impact on children and teenagers remains less understood.

What the study found

Researchers analysed three-day diet diaries and clinical health measures from over 4,700 participants at ages 7 and 13, as well as more than 2,500 participants followed to age 24.

Key findings include:

• At age 7, a longer eating window was associated with a higher body mass index z-score. A child’s body mass index z-score is a measure of how their body mass index differs from the average body mass index of a child of their age and sex. This finding suggests a small link between more extended eating and higher relative body weight in early childhood.
• At age 13, however, the pattern reversed: longer eating windows were associated with lower body mass index z-score, as well as:
  • Lower waist-to-height ratio
  • Smaller waist circumference
  • Lower diastolic blood pressure (the lower of the two numbers in a blood pressure reading, representing the blood pressure in between heartbeats)
  • Lower body fat percentage
• By age 24, those who had longer eating windows at age 13 showed lower body fat percentages, even more than a decade later.

Although the associations were modest, the findings suggest that rigid time-restricted eating may not always be beneficial for younger populations. However, further research is needed to fully understand these associations.

Reconsidering time-limited eating in youth

The researchers emphasise that, unlike in adults, time-restricted eating might not be the optimal strategy for children and adolescents, whose nutritional needs are closely tied to growth, development, and hormonal changes.

Jill Townley, lead author of the study, said:

“These results challenge the assumption that shorter eating windows will have similar effects in children and adolescents to those seen in adults.

“In adolescents, we found that a longer window for food intake was associated with healthier body composition and cardiovascular indicators, albeit with very small effects.

“The unexpected nature of these findings suggests further research is needed in these age groups.”

Why this matters

Time-limited eating has become a popular way to lose weight and improve metabolic health, but its application in younger age groups is less well researched. This study is among the first to examine how the timing of food intake, not just what or how much is eaten, relates to health outcomes over time in a general population of youth.

Given the small effect sizes, the authors caution against drawing strong clinical conclusions. Still, the research underlines the importance of studying dietary timing as part of broader public health and nutrition strategies for young people.

What’s next?

The researchers call for further investigation into the mechanisms linking eating patterns and health in youth, as well as randomised trials to explore how adjusting eating windows might – or might not – benefit this age group.