LIMITFOOD2 is a randomized clinical intervention study that investigates the effects of two different intermittent fasting protocols compared to a control group on the health of obese adults. A total of 90 participants will be randomized into three equally sized groups: a modified alternate day fasting, a time-restricted eating and a control group, receiving general weight-loss counseling.

The prevalence of overweight and obesity worldwide has risen considerably in the past century with more than one billion overweight persons, and about 600 million obese patients in 2015. Humans in modern societies typically eat at least three main meals per day and snacks around the clock. This change in eating pattern in terms of quantity and frequency leads to overconsumption of food and consequently to excess weight. Furthermore, obesity increases the risk of developing diabetes, cardiovascular disease and several types of cancer. The world health organization (WHO) has stated that there are 2.8 million deaths per year as a result of overweight and obesity.

In recent years, the concept of re-introduced fasting intervals in the form of intermittent fasting (IF) protocols became a popular alternative dietary strategy with the aim to achieve weight control and improve metabolic health. There are several different IF protocols, the most popular is time-restricted eating (TRE), which allows ad libitum (at one's pleasure) energy intake within a defined time period each time (6 to 12 hours). Another IF protocol is alternate day fasting (ADF), on 'feast days' one can consume food ad libitum, while on 'fast days' no or little food is consumed, feast and fast days alternate throughout the week. Animal studies and previous human clinical trials have provided evidence that various types of IF lead to weight loss and improved health markers. So far, interventional studies focused on the comparison of IF versus a control group, however only few studies compared different IF protocols directly. Given both the evidence for beneficial effects of IF as well as its growing popularity, it seems mandatory to reveal possible differences in the effectiveness of different protocols.

The present project will allow to directly compare two types of IF with each other and with a control group in obese participants. Furthermore, established and novel monitoring tools to track individual progress during IF are scarcely used so far but may become an important help in the future and thus, will be implemented in this trial.

Inclusion Criteria:

• Age between 18-50 years, both inclusive
• Obese, BMI between 30 and 40 kg/m^2 (obesity grade I or II), both inclusive
• Non-smoker
• Good knowledge of German or English language
• Stable weight change (change < +/- 3% current bodyweight) for 3 months prior to the study
• HbA1c < 6.5% without glucose lowering medication
• LDL-cholesterol < 4.6mmol/l without lipid lowering medication

Exclusion Criteria:

• Participants who have a fasting period of > 12h per day on a regular basis and do not eat at least three main meals per day.
• Current habitual use of dietary supplements (e.g., vitamins, minerals) and/or unwillingness to cease intake of dietary supplements.
• Antibiotics intake during 3 months prior to the study due to possible interference with metabolic parameters
• Food intolerances, allergies and sensitivities (severe food allergies) or dietary restrictions (e.g. vegan lifestyle)
• Acute or chronic infections, malignant disease, renal, hepatic (more than two-fold increased transaminases), pulmonary, neurological (epilepsy) or psychiatric diseases, manifested atherosclerosis, or any other disease precluding participation in the study.
• Diabetes
• Known alcohol, substance or drug abuse, concomitant medication
• More than four hours of physical exercise per week
• Women who are pregnant, breast-feeding or aiming to become pregnant during course of the trial
• Women and men on hormonal supplementation
• Women with an irregular menstrual cycle according to the FIGO criteria
• Therapy with antidepressants within the past 6 months
• Regular therapy with acetylsalicyclic acid or current medication to regulate blood sugar, blood pressure or lipids
• Participants likely to fail to comply with the study protocol
• Participants who do not give informed consent