Ketogenic Diet - a Randomized, Controlled, Cross-over Study
Condition: Healthy
Study type: Interventional

Summary: 
      The investigators planned study is a randomized, controlled exploratory study of a ketogenic
      and a NFA (National Food Administration) recommended diet. Study participants will be female
      nutrition students with both knowledge and interest in dietary surveys, in order to increase
      motivation and adherence. They will be provided with cooked food. The women should be weight
      stable and maintain their physical activity during the study, in order to evaluate how the
      diet itself affects various health parameters. The investigators intend to investigate diet
      specific biomarkers (small molecules involved in metabolism) in the blood, as well as blood
      lipids, body composition, gut microbiota, energy substrate utilization, exercise performance,
      resting metabolic rate, hormones, cognition and sweet cravings. In addition, the
      investigators intend to qualitatively study the experience of following both of these dietary
      regimes. The investigators intend to make a short and controlled study. The study is expected
      to reveal whether the ketogenic diet is a healthy or unhealthy diet in the short term. The
      investigators also expect that data from this study will be a helpful tool to measure diet
      adherence in future long-term studies.
    

Detailed description: 
      Aim: The aim of this randomized controlled exploratory study is to study effects of a
      ketogenic diet (a low carb - high fat (LCHF) diet) compared to a National Food Administration
      (NFA) recommended diet (NNR2012).

      Primary outcomes are blood lipids and diet specific biomarkers. Power calculations show that
      20 participants are needed to obtain significant results with 90% power at the 95%
      significance level for the primary outcome small-dense LDL (blood lipids). The investigators
      calculate that 20% of the participants will drop out before the end of the study, and
      therefore the investigators aim to recruit a total of 24 participants.

      Secondary outcomes are body composition, gut microbiota, energy substrate utilization,
      exercise performance, resting metabolic rate (RMR), hormones, cognition, sweet cravings, and
      the experience of following the two dietary regimes.

      Study design: Study participants will be female nutrition students with both knowledge and
      interest in dietary surveys, in order to increase motivation and adherence. The women should
      be weight stable and maintain their physical activity during the study, in order to evaluate
      how the diet itself affects various health parameters.

      Study participants will be provided with all food in the diet intervention. The amount and
      source of fat, protein and carbohydrates in the two diets are strictly defined; LCHF: Maximum
      25 g carbohydrates/day (approximately 5 E%), 20 E% protein and 75 E% fat (35 E% saturated
      fat). NNR2012: 50 E% carbohydrates, 20 E% protein and 30 E% fat (10 E% saturated fat).

      Study participants will be randomized with respect to their physical activity level to one of
      two study arms, with crossover design:

      Study arm 1: LHCF (4 weeks) --- washout (15 weeks) --- NNR (4 weeks) Study arm 2: NNR (4
      weeks) --- washout (15 weeks) --- LCHF (4 weeks)

      Study participants will eat each diet for four weeks. The different diets are separated by a
      washout period when they eat "as usual".

      Every morning during each four-week diet period the participants will measure their urine
      ketones by using urine ketone strips, weigh themselves and record their body weight. Any
      discrepancies in food intake will be recorded in a log book in which also the daily physical
      activity level is specified. Energy expenditure will be measured for three days during the
      four week periods using SenseWear activity meter (a validated and objective method) to see if
      energy intake matches energy expenditure.

      Baseline- and outcome measurements will be performed prior to and at the end of each
      four-week diet period.

      Qualitative measurements: When the whole diet study is completed and the research subjects
      have experience of eating both NNR and LCHF diet interviews will be conducted with some of
      the research subjects.

      The study is expected to reveal whether LCHF is a healthy or unhealthy diet in the short
      term. The investigators also expect that data from this study will be a helpful tool to
      measure diet adherence in future long-term studies.
    

Intervention name(s): Ketogenic diet for four weeks, then a 15 week washout, and finally a NFA recommended diet for four weeks; NFA recommended diet for four weeks, then a 15 week washout, and finally a ketogenic diet for four weeks.
Intervention type(s): Other; Other
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Investigator, Outcomes Assessor)
Primary purpose: Basic Science