New Research: Meal Timing and Body Fat

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A recent study in the Journal of Nutritional Sciences finds that small changes to your first and last meals of the day can lower body fat. 1

Scientists used “time-restricted feeding,” a form of intermittent fasting, in a 10-week study at the University of Surrey to evaluate the impact that altering meal times had on food intake, body composition, and lab markers for diabetes and heart disease. The study was led by Dr. Jonathan Johnston.

Subjects were divided into two groups -- one that was required to delay eating breakfast for an hour and a half and eat dinner an hour and a half earlier, and a control group that ate meals at their normal times. Participants had to provide samples of blood and complete food diaries before and during the 10-week trial period as well as complete a feedback questionnaire right after the study.

Unlike other diet studies, subjects were allowed to eat freely and were not advised to stick to a strict diet, as long as they ate meals within a certain window. This allowed researchers to evaluate whether this type of eating plan could be sustained in everyday life. 2

In the group that changed meals to a later breakfast and earlier dinner, subjects lost on average over twice as much body fat than the control group who did not change their eating times or habits. If larger studies on time-restricted feeding can be repeated, they may have greater impact on health.

Scientists in the study discovered that even though no restrictions were advised in the study group, subjects that altered meal times ate less food overall than the control group. Questionnaire replies confirmed a reduced food intake as 57% of subjects cited less appetite, fewer opportunities to eat, and a reduction in snacking, especially in the evening. It is unclear whether a longer fasting period was an additional factor in body fat reduction.

Researchers included questions regarding sustainability of the new eating times with participants. When asked, 57% of subjects said that the new times could not be sustained after the 10-week period due to family and social life. But 43% of subjects answered that they would continue the eating patterns if times were more flexible.

Johnston maintains "Although this study is small, it has provided us with invaluable insight into how slight alterations to our meal times can have benefits to our bodies. Reduction in body fat lessens our chances of developing obesity and related diseases, so is vital in improving our overall health. However, as we have seen with these participants, fasting diets are difficult to follow and may not always be compatible with family and social life. We therefore need to make sure they are flexible and conducive to real life, as the potential benefits of such diets are clear to see."

Johnston will use this pilot study to develop bigger, more comprehensive research on time-restricted feeding. More research needs to be conducted in this area as some animal studies show that intermittent fasting may raise the risk for diabetes by impacting insulin levels and damaging the pancreas. 3

For clinicians counseling clients on weight loss, reductions in body fat, or improvement in blood sugar and lipids, intermittent fasting may be worth a try but is not considered safe during pregnancy or for those at risk for/or suffer from eating disorders. Patients taking diabetes medication should be monitored closely for episodes of hypoglycemia. Medications may need to be adjusted to compensate for changes in meal times. 4

By Lisa Andrews, MEd, RD, LD


  1. Rona Antoni, Tracey M. Robertson, M. Denise Robertson, Jonathan D. Johnston. A pilot feasibility study exploring the effects of a moderate time-restricted feeding intervention on energy intake, adiposity and metabolic physiology in free-living human subjects. Journal of Nutritional Science, 2018; 7 DOI: 10.1017/jns.2018.13
  2. Ruth Patterson, Dorothy Sears. Metabolic effects of intermittent fasting. Annual Review of Nutrition. Vol. 37: 371-393. Aug, 2017.
  3. Ana Cláudia Munhoz Bonassa & Angelo Rafael Carpinelli. Intermittent fasting for three months decreases pancreatic islet mass and increases insulin resistance in Wistar rats. Endocrine Abstracts (2018) 56 P519 | DOI: 10.1530/endoabs.56.P519.
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