AIMS To determine the effect of high and low sucrose diets on liver fat in healthy adult men with liver fat levels below 5%

DESIGN Randomized, cross-over design with two 7-day dietary interventions separated by a 4 week wash-out period. Dietary intervention will be based on iso-energetic substitution of sucrose for starch in a weight-maintaining diet. The two experimental conditions are: high sucrose diet at 25% of total energy intake (this is approximately the 95th percentile for UK intake of non-milk extrinsic sugars (NMES)); and low sucrose diet at 10% of total energy intake. Otherwise the macronutrient balance in both conditions will be based on UK average habitual intake.

POPULATION 10 healthy males aged between 20 and 40 years, with a BMI between 20-25kg/m2, with normal liver fat levels (<5%) and fasting plasma glucose and no evidence of insulin resistance will be recruited. No pre-existing morbidity including cardiac, hepatic or renal disease, history of diabetes, hypertension or hyperlipidemia. Usual physical activity of subjects to range from sedentary to a maximum of meeting the UK minimum activity recommendations (30 min moderate exercise 5 d/week). Habitual alcohol intake of less than 2 units per day.

TREATMENT Pre-intervention: Participants will be asked to record habitual dietary intake by completion of a 7-day food diary and be asked to wear an accelerometer armband to assess physical activity before each intervention week. Resting energy expenditure will also be assessed by indirect calorimetry.

7 day dietary interventions: Participants will be resident at the clinical research facility at Hammersmith Hospital during each intervention week for 5 out of the 7 days and all food will be provided at the facility. At the weekends, participants will have to leave the unit but food will be provided for those two days so that the diet can be continued at home.

At the start and end of each 7 day intervention: Weight, height and waist circumference will be taken; percentage liver fat and total and regional body composition will be measured by MRI. Fasting and post prandial plasma glucose, insulin and lipids will be measured and blood pressure.

Inclusion Criteria:

Healthy men aged between 20 and 40 years with BMI between 20-25 kg/m2 and with normal liver fat levels (<5%), normal fasting glucose (less than 5.5mmol/l) and HbA1C less than 5.7% will be eligible to volunteer.

Exclusion Criteria:

• Type 1 diabetes, Type 2 diabetes, hypertension or hyperlipidaemia
• Gained or lost ≥ 3kg weight in the past three months
• Use of medication likely to interfere with metabolism, appetite regulation, glucose homeostasis and hormonal balance
• Regular consumer of sugar sweetened beverages
• Any chronic illness
• Cardiovascular, hepatic or renal disease
• Excess alcohol intake (>2 units per day)
• Exceeding UK minimum activity recommendation (30min moderate exercise 5d/wk)
• Current smokers (smoked within last 6 months)
• Any gastrointestinal disorder e.g. Crohn's disease, coeliac disease or irritable bowel syndrome
• A history of drug or alcohol abuse in the last 2 years
• Pancreatitis
• Unable to have MRI (eg. metallic or magnetic implants, claustrophobia)

6 weeks