IRREGULARITY OF MEAL PATTERN AND METABOLIC HEALTH

Abstract

The potential for an irregular, or chaotic, eating pattern which exhibits day to day variation has increased recently. Irregular eating may increase the risk of obesity and associated health consequences by possibly causing chrono-disruption because of the fluctuations in the timing of food intake disrupting entrainment of circadian patterns. This thesis 1. undertook a systematic review to identify the literature relating to meal pattern irregularity and obesity and associated negative health consequences, 2. developed a new methodology for characterising meal pattern irregularity and explored association with obesity and health outcomes (Study 1), 3. determined the potential impact of meal pattern irregularity on nitrogen balance (Study 2) and 4. investigated the feasibility of providing a hypo-energetic diet to participants with normal/overweight to explore day-to-day variation of energy expenditure, TEF, fasting blood glucose, fasting lipid profiles, fasting gut hormones, interstitial glucose concentrations and subjective appetite (Study 3). Methods 1. A systematic search was undertaken using relevant databases for studies with adults and children in which between day variability in meal pattern was measured, and related to body weight, metabolic syndrome components and cognitive function. 2. Two methods for characterising meal pattern variability were proposed using NDNS data in study. The first method used a variety of different meal pattern properties to describe the degree of irregularity in meal patterns. The second method involved the derivation of two indices relating to the energy consumption and time of eating, each with two threshold systems. 3. Using cross-over design, a randomized controlled trial with two 7-day intervention periods, separated by a wash- out period of three weeks was conducted on 14 healthy female participants to investigate the effect of irregular meal pattern on nitrogen balance 4. Study 3 had a randomised, parallel design with 7 days (pre-standardisation period) during which participants consumed their estimated energy requirement. Participants then adopted one of two meal patterns for the 14-day intervention period when they consumed a hypoenergetic diet, followed by a further 3 days (post-standarisation period) consuming their estimated energy requirement. 1 Results 1. The systematic review showed that many different methods in the literature for characterizing between day variability in meal pattern tended not to utilise all the potential properties of the meal pattern. Moreover, between day variability in meal pattern was associated with obesity and health outcomes including higher weight, reduced thermogenic response to meals and poorer academic achievement. 2. The two novel methods for characterising meal pattern irregularity in Study 1 suggested that day-to-day variation appears to be associated with obesity, dyslipidemia and hyperglycemia. However, the nature of the association in Method 2 was not consistent between the two indices as the Irregular time index showed the opposite relation to BMI, HDL cholesterol and HbA1c. Although the effect size in each model of the linear regression were small between 0.6% and 15%, the associations were statically significant. 3. The findings from Study 2 have indicated that the effect of meal pattern irregularity on nitrogen balance over 7-day period is not significant (P=0.091). 4. Study 3 has demonstrated that the protocol to test the hypo-energetic diet based on regular or irregular meal pattern on energy expenditure, metabolism and circadian rhythm is feasible and required some amendments. Conclusion Following a regular meal pattern might be a potential additional goal for body weight management as it seems to improve energy expenditure and insulin sensitivity which may indicate a favourable effect on insulin resistance and the risk of cardiovascular diseases. However further randomised controlled studies are required to confirm these results and elucidate the magnitude of the effect, hence potential clinical significance.