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ASSOCIATIONS OF CHRONOTYPE WITH DIETARY HABITS, OBESITY AND GENETICS : A population-based study in Finnish adults

Year: 2021
Type: dissertation
Study design: Observational Study
Abstract: Chronotype refers to preferences in timing the daily activities; accordingly, individuals can be divided from extreme morning to extreme evening types. The evening type has been associated with unhealthier behavior and higher morbidity and mortality risk than the morning type. Furthermore, twin studies have suggested genetic underpinnings behind chronotype trait. However, chronotype associations of dietary habits, obesity and genetics have not been thoroughly examined. The aim of this thesis was to study the associations between chronotype, dietary habits (overall diet quality, energy and macronutrient intake timing) and obesity (weight, body mass index [BMI], waist circumference, body fat percentage) and the interrelationships between these factors. This thesis additionally aimed to clarify the genetic basis of chronotype (clock gene analysis, genome-wide association study [GWAS] of chronotype, developing a genetic risk score [GRS] for chronotype). The study population included participants from the population-based National FINRISK 2007 (n=9958) and 2012 (n=9905) studies and the following sub-studies of FINRISK 2007: DIetary Lifestyle and Genetic determinants of Obesity and Metabolic syndrome (DILGOM) 2007 (n=5024), DILGOM 2014 (n=3735, follow-up) and National FINDIET 2007 (n=2054) conducted at the Finnish Institute for Health and Welfare. Chronotype was assessed with a shortened morningness–eveningness questionnaire. Overall diet was assessed with a validated food frequency questionnaire and measured with the Baltic Sea Diet Score (BSDS), which illustrates adherence to the healthy Nordic diet. Energy and macronutrient intake timing was assessed with 48-hour dietary recalls and 3-day food records. Anthropometric measures were based on measured and self-reported values. Statistical analyses were conducted with analysis of covariance and with linear and logistic regression. The evening type was associated with lower adherence to the healthy diet and with lower energy and macronutrient intake (except for sucrose [E%]) in the morning (by 10:00 a.m.) and higher energy, sucrose (E%), fat (E%) and saturated fat (E%) intakes in the evening (after 8:00 p.m.). Differences between morning and evening types in energy and macronutrient intake timing were even more pronounced at the weekend. Those with a higher tendency towards eveningness more likely had a lower baseline BMI in men but not in women. A higher percentage of evening-typed women had at least a 5% increase in weight and BMI than did morning-typed women during a seven-year follow-up period. These associations, however, attenuated after excluding participants with depression. When interrelationships between chronotype, dietary habits and obesity were examined, no evidence was found that the BSDS would mediate the association between chronotype and obesity or that chronotype would modify the association between the BSDS and obesity. Instead, higher evening energy intake was associated with a higher obesity risk independent of chronotype. Clock gene analysis revealed a novel association between chronotype and the NR1D2 gene. No genome-wide significant associations were found, but the genetic risk score based on 313 single nucleotide polymorphisms (SNPs) that have previously been associated with chronotype predicted the chronotypes in the present study population. In conclusion, despite unhealthier dietary habits (lower adherence to the BSDS, later energy intake timing) of evening chronotypes, evening types were not significantly more prone to obesity nor did chronotype play a role in the association between healthy diet/energy intake timing and obesity. Furthermore, a novel clock gene association was found with the NR1D2 clock gene, which has previously been demonstrated to have a role in carbohydrate and lipid metabolism. A GRS based on GWAS studies of chronotype may be a useful tool for capturing the genetic aspect of chronotype in different populations.
Language: English
Open Access status: green
OpenAlex ID: W3140135484
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