Award details

Extended Daily Fasting and Regulation of Energy Balance

Reference	BB/H008322/1
Principal Investigator / Supervisor	Professor James Betts
Co-Investigators / Co-Supervisors
Institution	University of Bath
Department	Department for Health
Funding type	Research
Value (£)	384,471
Status	Completed
Type	Research Grant
Start date	12/04/2010
End date	11/04/2013
Duration	36 months

Abstract

This study will examine how extended daily fasting as opposed to daily breakfast consumption might modify metabolism and behaviours such that a shift in energy balance can occur, with potential effects on health outcomes. The first phase of the investigation will quantify resting metabolism via indirect calorimetry and track changes in substrate oxidation and blood metabolites following a standardised breakfast under controlled conditions. The concentration of hormones known to be involved in regulation of metabolic rate, appetite and spontaneous physical activity (i.e. free thyroxine, adiponectin, cholecystokinin, total/acylated ghrelin, leptin and peptide YY) will also be determined over the hours leading-up to and after a subsequent test meal to determine voluntary energy intake at lunch. A second phase of testing will then commence, with participants randomly assigned either to a group that will fast until at least 12 pm daily or a group that consumed a prescribed energy intake before 11 am daily (both for a period of six weeks), thus extending initial laboratory-based assessments into a more externally valid setting. Combined heart-rate/accelerometers will be used during this intervention period to provide the first evidence related to free-living energy expenditure with such treatments. Participants will also be provided with weighed dietary food records during this time and be fitted with a continuous glucose monitoring system to assess 24-h glycaemic responses. Dual Energy X-ray Absorptiometry (DEXA) will be used before and after the intervention period to assess changes in total body mass and tissue distribution (i.e. fat versus lean mass), while oral glucose tolerance tests and adipose tissue biopsies will also be applied to assess insulin sensitivity both at a whole-body and tissue level. These tissue samples will also be analysed for the expression of genes relevant to appetite, physical activity, insulin resistance and chronic-low grade inflammation.

Summary

Much scientific research been directed towards an improved understanding of how breakfast may be related to population health. It has long been established that individuals who do not frequently consume breakfast are more likely to be overweight and suffer from a range of associated negative health outcomes such as hypercholesterolaemia, coronary heart disease and diabetes. Surprisingly however, little longitudinal research or evidence from randomised controlled trials is available to confirm the existence of any direct causal relationship (or mechanisms of effect) between breakfast and health. Given that people who usually skip breakfast also tend to adopt other less healthy lifestyle habits (e.g. higher fat/alcohol intakes, lower fibre/micronutrient intakes and a tendency to be less active), further research is therefore clearly warranted not only to establish whether there is a cause-effect relationship between breakfast consumption and health but also to determine the mechanism for this effect, whether it be via improved diet or increased physical activity. While many findings arising from this research certainly remain equivocal, the general pattern which is emerging is that the relative inclusion or omission of breakfast from the diet does not have a substantial impact on energy intake or aspects of resting metabolism. The only remaining possibilities are therefore either that breakfast increases physical activity or that any underlying metabolic effects may just take a period of weeks to occur. It is therefore interesting that no existing study has objectively and reliably measured physical activity habits in response to breakfast relative to extended daily fasting. To address these gaps in current understanding, the proposed study will therefore directly compare the effects of having or omitting breakfast from the diet, firstly in relation to the acute metabolic and behavioural (i.e. appetite) effects of a standardised breakfast relative to an extended fast on a given day and secondly in relation to the chronic effects of habitual consumption/omission of breakfast. The first phase of testing will reveal the extent to which resting metabolic rate and energy intake at lunch are affected under controlled laboratory conditions, while the second phase of testing will make use of recent technological advances to accurately gauge responses to each treatment under free-living conditions. For this second phase, half the study cohort will ingest a prescribed amount of energy before 11 am every day for six weeks, while the other half will extend their overnight fast until 12 pm every day for six weeks. Energy intake and energy expenditure will be monitored over this period using weighed food records and a novel physical activity monitoring system, respectively, while glucose concentrations will also be monitored continuously using a portable device. Following the 6 week intervention, an advanced form of X-ray analysis (DEXA) will be used to measure how each participant may change throughout the experiment in terms of their total body mass and fat/lean tissue composition. Small samples of sub-cutaneous adipose tissue will also be acquired before and after this intervention both to directly assess the sensitivity of this tissue to insulin with each feeding regimen and also to determine the expression of genes relevant to regulation of appetite/physical activity behaviours, insulin resistance and chronic low-grade inflammation. In relation to the latter, various markers of inflammation will also be measured in the blood given that these measures have been implicated in and therefore provide and indication of cardiovascular-disease risk. Finally, participants will repeat their acute breakfast trial exactly as was performed under the first phase of testing to determine whether the previously observed effects in terms of metabolic rate and energy intake at lunch may have been modified by prolonged exposure to each intervention.

Impact Summary

The prevalence of overweight and obesity in western societies have both increased dramatically over the past 4-5 decades (paralleled by a concomitant decline in breakfast consumption), an epidemic which is of primary concern given that excess body fat is known to be associated with the incidence of various cardiovascular and metabolic diseases, both directly as an independent risk factor per se but also indirectly simply as a symptom of either poor diet and or an inactive lifestyle. The most logical and direct benefit of the proposed work will therefore be to a large proportion of the general population for whom an effective weight loss strategy is required. This would be beneficial on an individual basis primarily from a health perspective but also often for aesthetic reasons and, with regard to the former, would therefore benefit the population as a whole. This benefit would be manifested directly as a reduced incidence rate of those negative health consequences associated with overweight and obesity but also via the indirect financial benefits in relation to the reduced costs of healthcare for such conditions. Importantly, unlike many other clinical treatments, this simple dietary modification would not necessarily require any commercial input other than simply to raise public awareness of the relative importance of habitually consuming breakfast, which could be communicated almost immediately via the public media once the findings are available. As such, the dissemination of findings from this study in the form of peer-reviewed articles will inform health policy with evidence-based recommendations regarding the role of breakfast in a healthy diet. Ultimately, it is hoped that the findings will therefore result in more individualised and scientifically valid guidance for the general public in terms of dietary weight management. Pending the outcome of the study, it is also anticipated that the publication of these findings will be of primary importance to industry in terms of the numerous independent companies with an interest in health related products, particularly breakfast foods. The current balance of scientific evidence in this area is very well cited in the general media and as part of advertising campaigns to support the health benefits of breakfast. From this perspective, the addition of causal and mechanistic data to the current evidence base is likely to be quickly detected by the organisations responsible for such media and will therefore further facilitate the communication of the main findings to the wider population for whom the message will be of greatest interest. Importantly, this application has been reviewed by colleagues at the Food Standards Agency (FSA) who have expressed support for the proposed work.

Committee	Research Committee A (Animal disease, health and welfare)
Research Topics	Diet and Health
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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