Modest changes to breakfast and dinner times can reduce body fat, a pilot study reports. During a 10-week study on 'time-restricted feeding' (a form of intermittent fasting), researchers led by Dr Jonathan Johnston from the University of Surrey investigated the impact changing meal times has on dietary intake, body composition and blood risk markers for diabetes and heart disease.
Participants were split into two groups – those who were required to delay their breakfast by 90 minutes and have their dinner 90 minutes earlier, and those who ate meals as they would normally (the controls). Participants were required to provide blood samples and complete diet diaries before and during the 10-week intervention and complete a feedback questionnaire immediately after the study.
Unlike previous studies in this area, participants were not asked to stick to a strict diet and could eat freely, provided it was within a certain eating window. This helped researchers assess whether this type of diet was easy to follow in everyday life.
Researchers found that those who changed their mealtimes lost on average more than twice as much body fat as those in the control group, who ate their meals as normal. If these pilot data can be repeated in larger studies, there is potential for time-restricted feeding to have broad health benefits.
Although there were no restrictions on what participants could eat, researchers found that those who changed their mealtimes ate less food overall than the control group. This result was supported by questionnaire responses which found that 57% of participants noted a reduction in food intake either due to reduced appetite, decreased eating opportunities or a cutback in snacking (particularly in the evenings). It is currently uncertain whether the longer fasting period undertaken by this group was also a contributing factor to this reduction in body fat.
As part of the study, researchers also examined if fasting diets are compatible with everyday life and long-term commitment. When questioned, 57% of participants felt they could not have maintained the new meal times beyond the prescribed 10 weeks because of their incompatibility with family and social life. However, 43% of participants would consider continuing if eating times were more flexible.
Dr Jonathan Johnston, reader in chronobiology and integrative physiology at the University of Surrey, said: "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.
"We are now going to use these preliminary findings to design larger, more comprehensive studies of time-restricted feeding.”
This pilot study explored the feasibility of a moderate time-restricted feeding (TRF) intervention and its effects on adiposity and metabolism. For 10 weeks, a free-living TRF group delayed breakfast and advanced dinner by 1·5 h each. Changes in dietary intake, adiposity and fasting biochemistry (glucose, insulin, lipids) were compared with controls who maintained habitual feeding patterns. Thirteen participants (29 (SEM 2) kg/m2) completed the study. The average daily feeding interval was successfully reduced in the TRF group (743 (SEM 32) to 517 (SEM 22) min/d; P < 0·001; n 7), although questionnaire responses indicated that social eating/drinking opportunities were negatively impacted. TRF participants reduced total daily energy intake (P = 0·019) despite ad libitum food access, with accompanying reductions in adiposity (P = 0·047). There were significant between-group differences in fasting glucose (P = 0·008), albeit driven primarily by an increase among controls. Larger studies can now be designed/powered, based on these novel preliminary qualitative and quantitative data, to ascertain and maximise the long-term sustainability of TRF.
Rona Antoni, Tracey M Robertson, M Denise Robertson, Jonathan D Johnston
[link url="https://www.surrey.ac.uk/news/changes-breakfast-and-dinner-timings-can-reduce-body-fat"]University of Surrey material[/link]
[link url="https://www.cambridge.org/core/journals/journal-of-nutritional-science/article/pilot-feasibility-study-exploring-the-effects-of-a-moderate-timerestricted-feeding-intervention-on-energy-intake-adiposity-and-metabolic-physiology-in-freeliving-human-subjects/9C604826401917A6CAD9CD10B72FEA32"]Journal of Nutritional Science abstract[/link]