The Effects of Diet on Mood, Cognition and Appetite
Condition: Mild Cognitive Impairment
MeSH terms: Cognitive Dysfunction
Study type: Interventional

Summary: 
      A previous study has found that the consumption of a high fat, low carbohydrate meal results
      in increased feelings of calmness, friendliness and an increase in subjective energy levels
      in comparison to a low fat, high carbohydrate meal. The purpose of this study is to
      investigate whether a high fat, low carbohydrate diet for a longer duration (of 2 weeks) can
      enhance or sustain these changes in comparison to a low fat, high carbohydrate meal.
    

Detailed description: 
      Research has shown that consuming breakfasts high in either fat or carbohydrates can affect a
      persons memory, mood and ability to concentrate (Benton & Parker, 1998, Politt & Mathews,
      1998). Our previous study investigating the effect of a high fat, low carbohydrate (HFLC)
      meal in comparison to a low fat, high carbohydrate (LFHC) meal found that the HFLC meal
      resulted in significantly increased feelings of calmness, friendliness and a reduction in
      feelings of anger, and an increase in subjective energy levels in comparison to a LFHC meal.
      However, the chronic effects of a HFLC or LFHC diet has not been studied. This purpose of
      this study is to investigate whether a 2 week diet high in either fat or carbohydrates
      improves cognition/memory and mood. It is hypothesised that the prolonged feeding of a HFLC
      diet will attenuate the response seen after a HFLC meal was provided.

      Twenty healthy women are required to attend the School of Biomedical Sciences on seven
      occasions.

      The first visit will involve screening tests for suitability for inclusion in the study and
      written, informed consent will be obtained. Weight, height and blood pressure will be
      measured and a 5ml blood sample will be collected for full blood count, urea, electrolytes
      and random blood glucose assessment. Subjects will be asked to complete questionnaires
      regarding general health, eating habits, mood and medical history. Following the screening
      visit, subjects will be asked to record their habitual food intake and physical activity
      pattern for a 3 day period (2 weekdays and 1 weekend day. They will then attend the
      laboratory on 6 further occasions, once for a familiarisation visit and for the 5 study
      visits.

      The familiarisation visit is required to ensure that subjects are comfortable and familiar
      with using the cognitive tests which will be administered.

      Subjects will be provided with a menu of foods to consume as their evening meal prior to
      study visits, based on 30% total energy expenditure. This meal will be based on foods the
      subject recorded in the completed food diary and will contain approximately 15% of total
      energy from protein, 55% from carbohydrate and 30% from fat. Before study visits subjects
      will be instructed to consume this standardised meal as their last meal of the day before
      20.00 on the previous evening. After they have consumed this meal they are instructed not to
      consume any foods or drinks apart from water until they arrive at the lab.

      Subjects will arrive (fasted) at the lab at 08.00 on the morning of each study visit. A
      cannula will be inserted retrograde into a hand vein, after prior infiltration at insertion
      site with 1% lidocaine. The hand will be placed in a heated box, and remain there throughout
      the trial, to obtain arterialised venous blood samples. The cannula will be kept patent with
      a slow infusion of 0.9% saline, and samples will be taken via a three-way tap.

      Subjects will then be either given a HFLC, or a LFHC breakfast, the order being randomised.
      The HFLC breakfast will be provided on study days before and after the HFLC diet
      intervention, and the LFHC breakfast will be provided on study days before and after the LFHC
      diet intervention.

      Water will be freely available throughout the day. Every 30 minutes subjects will be asked to
      complete a set of visual analogue scales designed to assess subjective mood and satiety, a
      15ml blood sample will be taken for the measurement of glucose, insulin, ghrelin, free fatty
      acids, glucagon, cholecystokinin (CCK), Glucagon-like peptide 1 (GLP-1), cortisol, adrenaline
      and noradrenaline. A 3ml sample will be taken every 15minutes for the first 90 minutes, for
      the analysis of insulin and glucose. A baseline sample for triglycerides and cholesterol will
      be taken at the beginning of each study visit. Cognitive tests (measuring attention reaction
      times and vigilance) will be completed 0, 45, 90 and 135 minutes minutes after the provision
      of breakfast. After 180 minutes, the cannula will be removed and subjects will be free to
      leave the lab.

      Subjects will be provided with either a HFLC diet or a LFHC diet to consume for 2 weeks.
      These diets will be designed to meet subjects energy requirements. After consuming the diet
      for 2 weeks (diets will comprise of 3 meals and 3 snacks per day), subjects will return to
      the laboratory for the second study visit. Subjects will be provided with a set of visual
      analogue scales to complete on days 4, 8 and 12 of the intervention period. Subjects will
      then return to their habitual diets for 2 weeks, before completing the second intervention.

      Subjects will also be asked to come to the laboratory for an additional study visit either 2
      days before visit 1 or two days before visit 3, where they will be consume their habitual
      breakfast instead of a HFLC or LFHC breakfast.

      During both the 2 week intervention periods, subjects will be asked to consume only the food
      provided, no other drinks, including alcohol and caffeinated drinks, may be consumed. If
      subjects are habitual tea/coffee drinkers then they may consume a maximum of 3 cups of
      tea/coffee a day (unsweetened, with milk from their daily allocation) and be asked to
      maintain this over both arms of the study.
    

Intervention name(s): High Fat Low Carbohydrate Diet; Low fat High Carbohydrate Diet
Intervention type(s): Other; Other
Intervention description(s): 55% total energy intake from fats, 17% from protein and 28% from carbohydrate; 20% total energy intake from dietary fats, 17% from protein and 63% from carbohydrate
Other intervention name(s): HFLC Diet; LFHC Diet
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Cognitive function; mood; women; high fat diet; high carbohydrate diet