Based on the typical Cantonese diet, the healthy Cantonese diet is developed according to the DASH diet and the balanced dietary pattern of the Chinese Dietary Guidelines 2016. In this diet, the main nutrients, dietary fiber, sodium, calcium, magnesium and potassium are set to achieve the healthy goal. Compared with the typical Cantonese diet, the healthy Cantonese diet is increased in fruit, vegetables, low-fat dairy products, whole grains, nuts and seeds, and reduced in salt, oil and sweets.

The typical Cantonese diet is a diet of what many Cantonese eat. In this diet, the main nutrients, dietary fiber, sodium, calcium, magnesium and potassium are set at the average dietary intake levels in Guangdong.

After a 1-week run-in period, the intervention group will eat the healthy Cantonese diet for 4 consecutive weeks. Free meals will be provided 3 times a day (breakfast, lunch, dinner). The actually intake of every meal for all subjects will be recorded to estimate their nutrients intake. All subjects will be advised to avoid eating other food, but they should inform researchers of what they eat if they eat food that we will not provide.

Changes of metabolic syndrome score in healthy Cantonese diet compared with changes of typical Cantonese diet. Metabolic syndrome score will be derived by standardizing and then summing the following continuously distributed indices of adiposity (waist circumference) to create a z score: hypertension (the average of systolic blood pressure and diastolic blood pressure); hyperglycaemia (fasting plasma glucose); insulin resistance (fasting insulin); fasting HDL-cholesterol × -1; and fasting triacylglycerol z score.

Changes of systolic blood pressure and diastolic blood pressure in healthy Cantonese diet compared with changes of typical Cantonese diet. Blood pressure will be measured by trained investigator at baseline, week 1, week 2, week 3 and week 4, and systolic blood pressure and diastolic blood pressure will be recorded.

Changes of blood lipid profile in healthy Cantonese diet compared with changes of typical Cantonese diet. Blood lipid profile (total cholesterol, TC; triglyceride, TG; LDL cholesterol, LDLc; HDL cholesterol, HDLc) will be tested by a validated biomedical analyses laboratory using vein serum at baseline and week 4.

Changes of glucose metabolism in healthy Cantonese diet compared with changes of typical Cantonese diet. Glucose metabolism (fasting plasma glucose and fasting insulin) will be tested by a validated biomedical analyses laboratory using vein serum at baseline and week 4 and insulin resistance index (HOMA-IR) will be calculated by [fasting insulin (mU/L) × fasting plasma glucose (mmol/L) ]/22.5.

Changes of blood biochemical marker in healthy Cantonese diet compared with changes of typical Cantonese diet. Blood biochemical marker (calcium, potassium, sodium, magnesium and phosphorus in mmol/L; uric acid in μmol/L) will be tested by a validated biomedical analyses laboratory using vein serum at baseline and week 4.