Biochemistry
Nutrition
Nutrition for MBBS: energy needs, balanced diet and fibre, marasmus and kwashiorkor, obesity risks and the glycaemic index, mapped to NMC codes BI8.1 to BI8.5.
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Nutrition
Nutrition for MBBS: energy needs, balanced diet and fibre, marasmus and kwashiorkor, obesity risks and the glycaemic index, mapped to NMC codes BI8.1 to BI8.5.
The nutrition chapter links biochemistry to public health. It covers energy requirements and the components of a balanced diet, the role of fibre and protein quality, protein energy malnutrition, obesity and its risks, and the nutritional value of everyday foods.
High-yield: Nutrition
- Dietary energy comes mainly from carbohydrate, fat and protein, yielding about 4, 9 and 4 kilocalories per gram respectively.
- The basal metabolic rate is the energy used at complete rest and forms the largest part of daily needs.
- A balanced diet supplies energy, essential amino acids, essential fatty acids, vitamins, minerals and fibre in adequate proportion.
- Dietary fibre adds bulk, slows glucose absorption, lowers cholesterol and prevents constipation.
- Protein quality depends on essential amino acid content; egg and milk proteins are reference standards of high biological value.
- Marasmus is severe energy and protein deficiency with wasting and no oedema; the child looks emaciated.
- Kwashiorkor is predominantly protein deficiency with oedema, a fatty liver, skin changes and irritability.
- The body mass index classifies underweight below 18.5, normal up to 24.9, overweight up to 29.9 and obese at 30 or more.
- Central or abdominal obesity carries a higher cardiometabolic risk than peripheral fat distribution.
- Obesity raises the risk of type 2 diabetes, hypertension, dyslipidaemia and cardiovascular disease.
- Fruits and vegetables provide vitamins, minerals, fibre and antioxidants with little energy density.
- The glycaemic index ranks foods by how quickly they raise blood glucose; low-index foods aid glycaemic control.
- Nitrogen balance reflects protein adequacy, being positive in growth and negative in starvation and severe illness.
- Trans fats raise LDL and lower HDL cholesterol, so they carry a higher cardiovascular risk than unsaturated fats.
- Micronutrient deficiencies of iron, iodine and vitamin A remain major public health problems in India.
Protein energy malnutrition
- **Marasmus:** Severe energy and protein deficit. Marked wasting, no oedema, emaciated look.
- **Kwashiorkor:** Mainly protein deficit. Oedema, fatty liver, skin and hair changes.
- **Body mass index:** Underweight below 18.5, normal to 24.9, overweight to 29.9, obese 30 or more.
- **Trans fats:** Raise LDL, lower HDL. Highest cardiovascular risk among fats.
NMC competencies in this chapter
- **BI8.1:** Importance of dietary components and of dietary fibre
- **BI8.2:** Types, causes and effects of protein energy malnutrition
- **BI8.4:** Causes, effects and health risks of overweight and obesity
- **BI8.5:** Nutritional importance of commonly used foods including fruits and vegetables
Frequently Asked Questions
What is the difference between marasmus and kwashiorkor?
Marasmus is severe deficiency of both energy and protein, causing wasting without oedema. Kwashiorkor is mainly protein deficiency and presents with oedema, a fatty liver and skin and hair changes.
Why is dietary fibre important?
Fibre adds bulk to stool and prevents constipation, slows glucose absorption to steady blood sugar, and helps lower blood cholesterol, all of which reduce long-term disease risk.
How is obesity defined by body mass index?
A body mass index of 30 or more defines obesity, with the overweight range from 25 to 29.9. Central obesity, measured by waist circumference, adds independent cardiometabolic risk.
What does the glycaemic index tell us?
It ranks carbohydrate foods by how quickly and how much they raise blood glucose. Choosing low-index foods gives a slower, steadier rise, which helps in diabetes and weight control.
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