The Effects of Diet on Mood, Cognition and Appetite
The Effects of Diet on Mood, Cognition and Appetite
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.
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.
Inclusion Criteria:

 -  female

 -  BMI 18.5-25kg/m2

 -  aged 18-45 years

 -  regular breakfast eaters

 -  regular menstrual cycle

 -  healthy

 Exclusion Criteria:

 -  Significant gastrointestinal disease, gastrointestinal surgery, diabetes or any other
 significant major medical morbidity

 -  History of significant eating disorder (anorexia, bulimia)

 -  Habitual dietary protein intake >20% of total energy intake

 -  pregnancy or breast feeding

 -  anaemia (Hb <11.5g/dL)

 -  random blood glucose concentration >8mmol/l

 -  no medication use other than contraception

 -  significant weight loss/gain (>14lb in previous 3 months)