Obesity and type 2 diabetes – Nutritional Deficiency and Health Disorders (Senior 3 Home Science) | Ganzaa

Nutritional Deficiency and Health Disorders

Lessons

Senior 3 · Home Science

Nutritional Deficiency and Health Disorders

4 lessons

Lesson 3 of 4

Obesity and type 2 diabetes

25 min

Let's begin

Malnutrition is not only hunger. In 2022 Rwanda's national survey of adults aged 18 to 69 found that 18.6% were overweight or obese, and among women the figure was 26%. Most of those adults have never had their blood sugar tested: in the same survey, 88.5% said they never had. Overweight raises the risk of type 2 diabetes, heart disease and some cancers, diseases that grow slowly over years and are mostly prevented by what is on the plate and how much people move. Worldwide, WHO counts 2.5 billion overweight adults in 2022, 890 million of them living with obesity.

Definition

Overweight and obesity: too much body fat, enough to harm health.

Body mass index (BMI): a person's mass in kilograms divided by the square of their height in metres: $\text{BMI} = \frac{\text{mass (kg)}}{\text{height (m)}^2}$ For adults, WHO calls a BMI of 25 or more overweight and 30 or more obesity.

Diabetes: a long-lasting disease in which the blood glucose (sugar) level stays too high, because the pancreas makes too little insulin, the hormone that lets cells take in glucose, or because the body does not respond to insulin properly.

Measuring body weight

BMI is a quick screening tool, not a diagnosis: a very muscular athlete may have a high BMI with little fat. A large waist is a second warning sign, because fat around the belly is the most harmful kind.

Causes of overweight

Taking in more energy than the body uses, day after day: large portions, fried snacks, sugary drinks and fatty foods.
Too little physical activity: long hours sitting, travelling by car or moto instead of walking.
Ready-made processed foods high in sugar, fat and salt, which are easy to over-eat.
Family habits, poor sleep, some medicines and inherited tendencies also play a part.

Type 1 and type 2 diabetes

Feature	Type 1	Type 2
What goes wrong	the pancreas makes little or no insulin	the body does not use insulin well, and later makes too little
Usual start	childhood or youth, often suddenly	adults, slowly; now also young people with obesity
Link to lifestyle	not caused by diet or weight	strongly linked to overweight, inactivity and unhealthy diet
Treatment	insulin injections every day, with a planned diet	healthy diet, activity and weight loss; tablets or insulin if needed

Warning signs: great thirst, passing urine often, tiredness, weight loss without trying, blurred vision and wounds that heal slowly. Anyone with these signs should have a blood glucose test at a health centre. In Rwanda, about 3% of adults had diabetes in the 2022 survey; worldwide, WHO counted 830 million people with diabetes in 2022.

TED-Ed, Emma Bryce: what the pancreas does. Watch the part on insulin and glucagon, the two hormones that keep blood sugar steady, and what happens when insulin is missing.

Food for preventing and managing obesity and diabetes

Half the plate vegetables, a quarter protein (beans, fish, eggs, lean meat), a quarter starchy food, preferably whole grain: sorghum, whole maize flour, brown rice, sweet potatoes with skins.
Regular meals at regular times, with no skipping and no large late-night meals; this keeps blood glucose steady.
Limit free sugars to less than 10% of daily energy, about 50 g (12 level teaspoons) for an adult eating about 2000 kcal a day, and ideally under 5% (WHO). Free sugars include sugar added to tea and porridge, sweets, soft drinks, and honey and fruit juice.
Whole fruit instead of juice: the fibre slows the release of sugar.
Cook with less fat: boil, steam, grill or bake instead of deep-frying; measure oil with a spoon.
Move: WHO advises at least 60 minutes of moderate to vigorous activity a day, on average, for young people aged 5–17, and 150–300 minutes a week for adults.

Worked example

Worked example 1: calculating BMI. Mr Habimana is 1.60 m tall and has a mass of 72 kg. Find his BMI and its WHO category.

$\text{BMI} = \frac{72}{1.60^2} = \frac{72}{2.56} \approx 28.1$
28.1 lies between 25 and 29.9, so he is overweight (Figure 3).
For a BMI of 24.9 at his height, his mass would be $24.9 \times 2.56 \approx 63.7$ kg, so a gradual loss of about 8 kg would bring him into the normal range.

Worked example

Worked example 2: sugar in one drink. A soft-drink label says 10.6 g of sugar per 100 mL. How much sugar is in a 500 mL bottle, and how does it compare with WHO's limit of about 50 g a day?

$\text{sugar} = 10.6\,\mathrm{g} \times \frac{500\,\mathrm{mL}}{100\,\mathrm{mL}} = 53\,\mathrm{g}$
At about 4 g per level teaspoon, that is about 13 teaspoons.
One bottle alone is more than the whole day's limit of free sugars. Water, or milk, is the better drink.

Warning

Be careful with weight and food. Teenagers are still growing: crash diets, skipping meals and "slimming" teas or pills can cause anaemia, weak bones and eating disorders. A young person worried about weight should see a health worker. Never tease anyone about body size; it harms health and does not help. A person with diabetes who becomes shaky, sweaty and confused may have low blood sugar: if they are awake and can swallow, give them a sugary drink or sweets at once, and get medical help if they do not recover quickly.

Tip

Exam tip. Square the height, not the mass, and keep the height in metres: 160 cm = 1.60 m. Give the BMI to one decimal place and then name the category.

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Practice

Write the formula for BMI and give the WHO adult cut-offs for overweight and obesity.
Give three differences between type 1 and type 2 diabetes.
List four warning signs of diabetes.
Calculate the BMI and category for (a) an adult 1.75 m tall with a mass of 60 kg; (b) an adult 1.50 m tall with a mass of 70 kg.
An adult is 1.70 m tall. Above what mass does the BMI reach 25?
Plan a day's meals for an adult with type 2 diabetes, using local foods.
A school canteen sells soft drinks, doughnuts and chips at break. Evaluate the effect on students' health and propose a healthier menu that students would still buy.

Show answersHide answers

$\text{BMI} = \frac{\text{mass (kg)}}{\text{height (m)}^2}$ ; overweight: 25 or more; obesity: 30 or more.
Type 1: little or no insulin made; usually starts in childhood; not caused by lifestyle; needs daily insulin. Type 2: insulin not used well; usually starts in adults; linked to overweight, inactivity and diet; managed first by diet, activity and weight loss (any three differences).
Great thirst; passing urine often; tiredness; weight loss without trying; blurred vision; slow-healing wounds (any four).
(a) $\frac{60}{1.75^2} = \frac{60}{3.0625} \approx 19.6$ : normal weight. (b) $\frac{70}{1.50^2} = \frac{70}{2.25} \approx 31.1$ : obesity.
$25 \times 1.70^2 = 25 \times 2.89 = 72.25$ kg, so about 72 kg.
Example: breakfast of sorghum porridge without added sugar, with milk, and an egg; lunch of beans, a small portion of brown rice or sweet potato, and a large serving of cooked greens and tomato salad; an orange as a snack; supper of fish or beans with vegetables and a small portion of ugali; water to drink. Meals at regular times, little oil and no sugary drinks.
These foods are high in sugar, fat and energy and low in fibre and micronutrients; eaten daily they lead to weight gain, tooth decay and a higher risk of diabetes later. A healthier menu: fresh fruit, boiled maize or groundnuts in small packs, bean samosas baked rather than fried, plain milk or water; keep prices low and make the healthy choice the easy one.

Sources and credits

Lesson text, Figure 3, table, worked examples and practice: written by Ganzaa. The drink label in Worked example 2 is illustrative.
Rwanda figures: Second Rwanda Non-Communicable Diseases Risk Factors Study (STEPS) 2021–2022, key findings, Rwanda Biomedical Centre (RBC). World figures and advice: Obesity and overweight (2025), Diabetes (2024) and Healthy diet (2026), WHO fact sheets; WHO guidelines on physical activity and sedentary behaviour, 2020. Low blood sugar first aid: European Resuscitation Council Guidelines 2025: First Aid, Djärv T. et al. Summarised in Ganzaa's own words.
Video: What does the pancreas do? - Emma Bryce, TED-Ed, embedded from YouTube.

1Measuring body weight

2Causes of overweight

3Type 1 and type 2 diabetes

4Food for preventing and managing obesity and diabetes

Measuring body weight

Causes of overweight

Type 1 and type 2 diabetes

Food for preventing and managing obesity and diabetes