Københavns Universitet
Uafhængig af ledelsen


Phd defence: Natasja Bjerre Martinsen

Ph.d.-forsvar — PhD defence for Natasja Bjerre Martinsen, Department of Food and Resource Economics, University of Copenhagen.


Date & Time:

Auditorium A2 – 82.01, Thorvaldsensvej 40, ground floor, 1958 Frederiksberg C.

Hosted by:
Department of Food and Resource Economics (IFRO), University of Copenhagen


Title of thesis
Squeezing time to lose weight
A qualitative longitudinal study of practicing time-restricted eating in daily life among individuals with overweight or obesity
The increasing prevalence of overweight and obesity is one of the largest public health and societal concerns today, and its many consequences for both individuals and society include an increased risk of developing non-communicable diseases such as type 2 diabetes (T2D). Despite numerous attempts globally, no country has managed to reverse the burden and identify successful, longterm strategies to reduce the incidence of overweight and obesity. This emphasises the need for new and sustainable approaches to reducing body weight. Intermittent fasting, such as time-restricted eating (TRE), has received increased attention in recent years. TRE extends the daily fasting period by limiting the daily eating window to, for example, 8-10 hours, usually without dietary restrictions. However, there is a lack of knowledge about the practice of TRE in daily life, which serves as the underlying motivation for this PhD thesis.

The overall purpose of the thesis is to investigate experiences with practicing TRE in daily life among individuals with overweight or obesity at risk of T2D who aim to lose weight. Specifically,

their performance and maintenance of TRE (the RESET [Restricted Eating Time] study) in daily life is examined during a three-month intervention and a three-month follow-up period. The focus is on examining the importance of incorporating social and daily contexts into the design of TRE interventions.

The thesis is based on a qualitative, longitudinal study and organised into four coherent studies. I conducted individual interviews and included weight loss data from three time points (baseline, end of intervention and end of follow-up period) to follow participants’ experiences with TRE over time. I use social practice theory as an overall theoretical framework and the concept of time and the concept of career in my data analyses.

Across the four studies, this thesis finds that participants perceive TRE positively. They do not significantly change their preferences for food and beverages but become more aware of time and plan their intake more carefully. In addition, I find individual variations in the practice and maintenance of TRE, which are influenced by daily circumstances. Participants who successfully integrate TRE into their daily routines manage to reorganise activities, maintain a consistent daily rhythm and regular meal structure, and recognise it as a strategy that can lead to results other than weight loss. Social support, especially from partners, also helps to ensure successful practice and maintenance and lead to weight loss. Lack of social support, living alone, collective rhythms avoidance of social evening events, feelings of shame, and an overriding focus on losing weight are challenges to practicing and maintaining TRE and hinder weight loss. Daily life rhythms that are too structured with no room for flexibility or minimally structured both pose a challenge to practicing TRE and achieving weight loss.

In conclusion, this thesis finds that TRE has the potential to become a useful strategy; however, it faces challenges similar to those of traditional weight loss strategies. Findings emphasise that the TRE intervention fails to account for the complex interplay between time and daily practices, often resulting in disruptions in both eating patterns and the organisation and rhythm of daily and social activities. Sustaining strict TRE is challenging because it necessitates more than simply altering eating times. Individualised support and customised guidance are essential to integrating TRE into daily routines, as is incorporating a broader understanding of daily life context in its design. This thesis suggests viewing families as the units of intervention and taking social conventions into account to improve individual adaptation to the TRE concept and processes of adjusting daily life activities to TRE. Although the specific combination of influential aspects is not yet fully understood, understanding situational contexts is crucial for tailoring food timing interventions like TRE. Additionally, collective rhythms require further investigation because they can interfere with the timing of eating regardless of individual preferences.

Sign up for a link and passcode for online hybrid zoom participation:

Please contact Natasja Bjerre Martinsen Natasja Bjerre Martinsen natasja.bjerre.martinsen@regionh.dk 10 August Month – 22:00 (CET), at the latest.

Department of Food and Resource Economics (IFRO), University of Copenhagen

Professor Lotte Holm, Department of Food and Resource Economics (IFRO), University of Copenhagen

Senior Researcher, Nanna Folmann Hempler, Copenhagen university Hospital, Steno Diabetes Center Copenhagen

Assessment Committee:
Associate professor Kia Ditlevsen, Department of Food and Resource Economics, University of Copenhagen

Professor Pernille Tanggaard Andersen, University of Southern Denmark

Senior lecturer/Associate professor Nicklas Numan, University of Uppsala, Sweden

Master of Ceremony
Professor Mette Weinrich Hansen, Department of Food and Resource Economics, University of Copenhagen

Request a copy of the thesis
If you are interested in a full copy of the thesis, please contact the PhD student or the PhD Secretary milton@ifro.ku.dk .