Nutrition Assessment and Dietary Guidance: Cut-offs, Indicators and the DRI Framework
This domain tests how you establish nutritional status and translate it into advice using Chinese reference standards. Items combine anthropometric cut-offs, biochemical and clinical indicators, the strengths and weaknesses of dietary intake methods, and the DRI framework with the Chinese Dietary Guidelines and Food Pagoda.
Anthropometry (Chinese adult cut-offs)
- BMI = weight (kg) / height (m) squared. China: below 18.5 underweight, 18.5-23.9 normal, 24.0-27.9 overweight, 28.0 and above obesity. The WHO 25/30 thresholds are not the ones to apply here.
- Waist circumference: 90 cm or more in men, 85 cm or more in women indicates central obesity (metabolic syndrome uses 85/80 cm).
- Under 5 years use the WHO Child Growth Standards; 5-18 years use Chinese BMI-for-age and height-for-age curves; head circumference is measured under 3 years.
Biochemical and clinical assessment
- Albumin has a long half-life (about 20 days) and tracks inflammation more than recent intake; prealbumin (transthyretin, about 2 days) is more sensitive but also falls with inflammation, so read CRP alongside.
- Iron: serum ferritin below 15 micrograms/L indicates depleted stores in adults, but inflammation raises ferritin; transferrin saturation adds specificity. Anaemia in China: haemoglobin below 130 g/L in men, 120 g/L in women.
- Clinical signs: Bitot spots and xerophthalmia (vitamin A), angular stomatitis and cheilosis (riboflavin), goitre (iodine), bow legs (vitamin D), peripheral neuropathy (thiamin).
Dietary intake methods
- 24-hour recall: fast and low burden, depends on memory, one day is unrepresentative - repeat it.
- Weighed food record: most accurate, high respondent burden, reactivity.
- Food frequency questionnaire: captures habitual intake, needs validation against a reference method, suited to epidemiology.
- Food balance sheets and household surveys: population level only.
DRI framework
The EAR is the average requirement; the RNI is set at EAR plus 2 SD to cover 97-98% of the population; the AI is used when an EAR cannot be set; the UL is the tolerable upper intake; the AMDR gives acceptable macronutrient ranges. China adds PI-NCD values to prevent noncommunicable disease: salt below 5 g/day, cooking oil 25-30 g/day, added sugar below 50 g and ideally below 25 g/day.
Worked example
A woman 1.65 m tall weighs 68 kg. BMI = 68 / 2.7225 = 24.98, which is overweight by the Chinese cut-off (24.0) even though it is normal by the WHO cut-off (25 is the boundary, and 24.98 rounds to 25). Correct exam answer: overweight, advise a modest energy deficit plus 150 min/week of moderate activity, and do not label her obese.
Traps that cost marks
Applying WHO 25/30 instead of 24/28. Using BMI for pregnancy, athletes or children. Treating albumin as a marker of intake. Reading the RNI as an average requirement rather than a near-total coverage value.