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expert reaction to study looking at time-restricted eating and weight loss in people with metabolic syndrome

Research, published in Cell Metabolism, reports that time-restricted eating may have benefits for people at risk of developing diabetes and other severe health issues. 


Prof Alexandra Johnstone, Rowett Institute, University of Aberdeen, said:

“The paper from the Salk Lab led by Dr Satchidananda Panda in the USA develops the theme of time restricted feeding (eating for 10 hours a day) in humans.  This group have previously published tantalising data from studies in mice show that mice fed a high-fat diet ad libitum, albeit within a time-limited feeding period (8-12 hours in 24h), have reduced adiposity and liver steatosis, as well as improved glucose tolerance and reduced cholesterol levels, compared with mice fed ad libitum over 24hrs; importantly, these improvements occurred in the absence of changes in energy intake.

“This newly published work in 19 overweight subjects suggest that optimal timing of meals can improve indices of metabolic health with a minimal 3% weight loss.  The main limitation is the lack of a control group to contrast findings.  This study reports that subjects reduced calorie intake by 8%, in comparison to their baseline, so it is not clear if the metabolic health improvements are due to being in a small negative energy balance or timing of eating per se.  Future work to investigate the effects of time-restricted feeding providing controlled diets at energy balance would help tease this out.  They used an app to record food intake over 12 weeks, so there is no information on nutrient intake is provided, with only ‘breakfast score’ mentioned.

“This study replicates what some other shorter-term other studies have found, that altering timing of eating can impact on energy balance and indices of metabolic health.”


Dr Jenna Macciochi, Lecturer in Immunology, University of Sussex, said:

“Metabolic syndrome in some people is associated with overconsumption of energy leading to changes their body composition by accruing proportionately much more fat than lean mass.  This is associated with an increase in insulin resistance.  Significant improvements in metabolic syndromes have been seen in previous research even after moderate or modest weight loss and this is primarily thought to be due to reduction of fat mass.

“This is a small study but critical in that is it the first step in translating what we know from experimental animal studies to be true in humans.  It is encouraging that some participants continued for up for one year because compliance is always a challenge with any kind of diet or lifestyle modification.  Importantly it enabled people to self select the eating window, rather than skipping meals.  A unique feature of this study is that participants could self-select the 10 hour eating window.  This is important because the previous studies that the authors cite in healthy individuals used a predetermined 10 hour eating window and the participants found this harder to stick to.  Adherence is a big plus for this study since that is one of the hardest things about any kind of weight loss practice.

Does the press release accurately reflect the science?

“Yes, I’d say the press release did a good job but it should emphasise that it did not look at calorie content of food.  Since being in a calorie deficit is the most effective way to lose weight and by reducing the eating window is may be easier to get into a deficit by having less opportunity to eat, its hard to say if time-restricted eating is any more effective that any weight loss strategy.  The only benefit is perhaps compliance.

Is this good quality research?  Are the conclusions backed up by solid data?

“Yes the data seems solid for the small size.

How does this work fit with the existing evidence?

“It builds nicely on the evidence in mice but it is a very small study and I think needs to be repeated by being equicaloric so that the effects of time-restricted eating can be disentangled from weight loss by calorie reduction.

Have the authors accounted for confounders?  Are there important limitations to be aware of?

“The authors acknowledge the other confounder (aside from the effects just being through calorie reduction) as changes to behaviour, i.e. participants might have engaged with other healthy behaviours because of their involvement in the study and we cannot confirm that participants logged their food in a 100% representable way.

What are the implications in the real world?  Is there any overspeculation?

“It’s possible to over speculate that time-restricted eating is a magic bullet to health whereas it may be that it’s just though calorie restriction.  On the flip side, for people who are struggling with fad diets it may be a useful tool and help compliance.”


Dr Duane Mellor, Registered Dietitian and Senior Teaching Fellow, Aston Medical School, Aston University, said:

“This was an interesting but small uncontrolled and non-randomised study which only included 19 people.  It does provide some evidence, but as there is no control group or randomisation it is very hard to tell if people did better following time restricted eating (limiting all there eating in a day to 10 hours) than if they had followed another type of diet.

“What we do know is that often in weight loss studies that are relatively short term, like this one, being in a study and the support it provides can help people change their behaviour to improve their health, lose weight and reduce their risk of developing type 2 diabetes and heart disease.  In the case of this study there are lots of limitations, not just the lack of a control group – a key one being that the act of recording food intake has been shown in other studies to reduce calorie intake and help with weight loss.

“Also, although lots of tests were done on the participants, it seems unclear how they justify the conclusion that improvements were seen independent of weight change as there simply was not a big enough number of people to make this assessment.

“We can’t quite claim from this study that time-restricted eating is an alternative to calorie counting – this approach like many is just a different way to limit food and therefore calorie intake.  Time restrictive eating as described in this paper is not a new as the paper seems to claim – as a dietitian with over two decades of experience working with weight management and type 2 diabetes in clinics and research, it is just one of a number of approaches.  We know that a range of diets can help weight management, risk of developing type 2 diabetes and managing diabetes from very low calorie meal replacements, through Mediterranean and vegan diets as well as low carb and keto plans – – as long as the diet is carefully planned so it is nutritionally appropriate – along with this studies time limited eating.  So any dietary approach which is part of a well-planned eating plan and lifestyle can improve health.  Hopefully, we can see this in the follow up study that these researchers are working on, but until then if anyone is planning to change their diet, they should look to change it to one they can enjoy and stick to, be that time restricted or one of a number of approaches which are supported by evidence, and seek advice from their doctor if they take medication and a dietitian to tailor their food intake to their tastes.”


Dr Gabriela da Silva Xavier, Senior lecturer in cellular metabolism, University of Birmingham, said:

Does the press release accurately reflect the science?

“The press statement omitted mention of the limitations of the study, which the authors discussed in the final section of the paper.  For example, the press release did not mention that the participants consumed fewer calories during time-restricted eating than at baseline, which could have contributed to the weight loss.  This reduction of calorie intake could be due to time-restricted eating, or to the raised awareness of calorie intake in the participants as a result of the design of the study.  Also, in this study, calorie intake was a self-reported value; a more rigorous way design to monitor this would be to conduct the tests in a controlled setting.  The latter is difficult to do but is needed to prove the point.

Is this good quality research?  Are the conclusions backed up by solid data?

“This is good quality research.  The researchers talk about their findings fairly and discuss the limitations of the study (and what could be done to address these shortcomings in future studies).

How does this work fit with the existing evidence?  Have the authors accounted for confounders?  Are there important limitations to be aware of?

“The authors have a long-standing interest in this area of research and their current findings are largely in line with their previous findings and that of other researchers in the field.  The major advancement in this work is data obtained from participants who have metabolic syndrome.  The authors have accounted for confounders and candidly discussed the limitations of the work, which was not particularly covered by the press release.

What are the implications in the real world?  Is there any overspeculation?

“The authors themselves acknowledge the limitations of the study and have made proposals for future work to determine the mechanisms that may have led to the improved metabolic profile of the participants on time-restricted eating.  They discussed many potential areas of future interest.  One area that may be worthy of attention, and is not particularly discussed in the paper, is the potential involvement of the endocrine system, particularly the hormones (e.g. glucagon) that are involved in regulating the fasted state, and how these may impact on mobilisation of fuel stores, and fuel usage and partitioning.”


Dr Katarina Kos, Senior Lecturer in Diabetes and Obesity, University of Exeter, said:

“The study shows that 19 people with increased risk of heart disease willing to reduce their food intake to an eating window of less than 11 hours could do so for 12 weeks and lose weight without skipping breakfast.  Half a stone of weight loss will as expected improve factors which make up metabolic syndrome, which is also known as the ‘Deadly Quartet’.  Its elements and key contributors to heart disease, apart from high body weight, or more specifically large waist, are high blood pressure, high cholesterol and elevated blood sugar.  We know from large lifestyle change studies that by achieving weight loss, blood sugar, blood pressure and blood lipids will also improve.  What we do not know is whether the same, probably rather motivated people would have done equally well with another weight loss intervention.  There is no control group which would allow for a comparison with no intervention, and no other type of intervention has been looked at, so we can’t know from this study which intervention the participants would prefer.

“For those who are concerned about their weight, the study shows that it is safe to stop having calories after a certain time in the evening, e.g. all eating and drinking except water.  And the three main meals of the day can safely be taken within an eating window of 10 to 11 hours.”


‘Ten-hour time-restricted eating reduces weight, blood pressure, and atherogenic lipids in patients with metabolic syndrome’ by Michael J. Wilkinson et al. was published in Cell Metabolism at 16:00 UK time on Thursday 5 December 2019.

DOI: 10.1016/j.cmet.2019.11.004


Declared interests

Prof Alexandra Johnstone: “None.”

Dr Jenna Macciochi: “No conflicts of interest.”

Dr Duane Mellor: “Nothing.”

Dr Gabriela da Silva Xavier: “I have no interests to declare.”

Dr Katarina Kos: “I have no conflict of interest.”

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