Exercises: A healthy diet

Name the groups of nutrients that a complete diet must include (proteins, carbohydrates, lipids, vitamins, mineral salts and water) and state a general function of each group in the body.

The food wheel shows several food groups labelled with letters, with larger sectors indicating a greater presence required in the daily diet. State which letter occupies the sector that should dominate our diet, which food group it corresponds to, and which letter indicates the group whose consumption should be occasional.

Explain why breakfast is considered an important meal, especially for school-age children, and describe a balanced breakfast indicating which nutrients are provided by each food item you include.

Explain the difference between food and nutrient, and give two examples of each concept.

Name the five meals a day that are recommended and explain why it is advised to spread food intake over several meals instead of one or two very large ones.

Explain what general function proteins have in an adolescent's body and cite three protein-rich foods.

State whether these statements are true or false and justify your answer: a) water is considered a nutrient even though it provides no energy; b) vitamins must be taken in large quantities to have an effect; c) pulses provide proteins and carbohydrates.

Explain why water is the nutrient we need to replace most often, and what happens to the body if it loses more water than it takes in.

Analyse this one-day menu: breakfast, a pre-packaged pastry and a soft drink; lunch, a burger with chips and a soft drink; dinner, pizza. Point out what problems it presents from the perspective of a balanced diet and suggest three specific changes to improve it.

The Mediterranean diet is considered a healthy model. Describe its main characteristics (predominant foods, primary fat source, consumption frequency for each group) and compare it with the typical diet of many teenagers today.

A 14-year-old female athlete needs about $2200\ \text{kcal}$ per day. If her breakfast provides about $450\ \text{kcal}$, calculate what percentage of her daily energy intake is covered by breakfast and reason whether it complies with the recommendation that breakfast should provide around $25\ \%$ of daily calories.

Compare a plate of lentils with vegetables with a portion of nuggets with chips: which nutrients each option provides, which fits better into a balanced diet, and why it is not about banning foods but about watching how often they are eaten.

Explain what ultra-processed foods are, how we can recognise them when shopping, and why their consumption should be limited even though they are tasty and cheap.

A teenager who trains daily wants to take protein shakes "like the influencers". Explain what the real needs of an athlete of his age are, whether a varied diet covers them, and what risks taking supplements without professional supervision has.

Explain what useful information the label of a packaged food offers (ingredients list and nutrition table) and how you would use it to compare two yoghurts on the shelf and choose the healthier one.

A student has only a glass of milk for breakfast and mid-morning has an energy and concentration "slump". Explain what may be happening to them and propose a complete breakfast, justifying what each food provides.

A supplement company promotes snack bars claiming they contain "$100\ \%$ of the non-essential nutrients your body needs", and asserts that thanks to this "it is no longer necessary to worry about eating fruit, vegetables, or legumes".\na) Scientifically refute this advertisement by explaining the difference between an essential and a non-essential nutrient, and give two examples of each group.\nb) Predict what biological consequences a person who based their diet solely on these bars would suffer, and justify why no single food—no matter how complete it is advertised to be—can replace a varied diet.

Imagine that you observe the following changes in a $14$-year-old classmate: they systematically skip recess snack saying they already ate at home, show constant worry about the calories in any food, have noticeably lost weight, and when the group suggests eating pizza, react with distress and isolate themselves.\na) Interpret these signs and deduce what type of eating disorder (ED) could be developing, comparing its main characteristics with those of bulimia.\nb) A friend suggests: "Let's not say anything to anyone; it's just a lack of willpower, it will pass". Refute their stance using biological and psychological arguments, and design a responsible action plan to seek immediate professional help from the school environment.

The nutrition label on a packet of biscuits indicates that every $100\ \text{g}$ contains $20\ \text{g}$ of fat, $65\ \text{g}$ of carbohydrate (of which $30\ \text{g}$ are sugars) and $6\ \text{g}$ of protein. The WHO recommends that free sugars should not exceed $10\ \%$ of daily energy. Knowing that $1\ \text{g}$ of sugar provides about $4\ \text{kcal}$ and that a teenager consumes about $2200\ \text{kcal}$ per day, calculate how many grams of these biscuits would reach that limit if they were the only source of sugar for the day, and comment on the result.

In a study on school health in a municipality, two seemingly contradictory pieces of data were obtained: $92\ \%$ of secondary school students pass an exam on the food wheel and healthy diet, but the rate of childhood overweight and obesity in that same school has risen from $18\ \%$ to $31\ \%$ in a decade. The neighbourhood report adds that within a $300\ \text{m}$ radius there are six cheap fast-food outlets and no fresh fruit shops.\na) Analyse this paradox and justify why the increase in childhood obesity cannot simply be explained as an "individual lack of information", linking it to the concept of an obesogenic environment.\nb) Design three well-founded intervention measures to curb this trend: one that depends on the student themselves, another that must be implemented within the family, and an organisational one for the school.

Lucía ($14$ years old), in the midst of her pubertal growth spurt, has decided to follow a vegan diet. Her usual daily menu consists of toast with jam for breakfast, white pasta with tomato sauce for lunch, and a lettuce and cucumber salad for dinner. After two months, she goes to the doctor complaining of extreme fatigue and weakness.\na) Critically analyse Lucía's menu: identify what serious deficiencies it presents (taking into account the quality of proteins, iron, and vitamin $\text{B}_{12}$) and explain why its current design puts her development at risk.\nb) Redesign her full-day menu using plant combinations that provide complete proteins and optimise iron absorption, and point out which nutrient will strictly require pharmacological supplementation.

A student consumes a bag of salty snacks ($1,5\ \text{g}$ of salt) and a cured ham sandwich ($2\ \text{g}$ of salt) mid-morning. The WHO sets a maximum daily limit of $5\ \text{g}$ of salt for adults (for teenagers it is even lower); use it as the reference.\na) Calculate what percentage of the maximum daily limit they have covered with just that snack and infer what will happen to their sodium balance by the end of the day if we add the salt from their main meals.\nb) Table salt (sodium chloride) provides no energy in the form of calories. Justify then, using the process of osmosis and fluid retention in the internal environment, why an excessive and chronic intake of salt overloads the circulatory system and raises blood pressure.

A can of sugary soft drink ($330\ \text{ml}$) and two whole oranges provide practically the same amount of simple carbohydrates (about $35\ \text{g}$). However, health guidelines advise against the soft drink because it provides "empty calories", while they recommend the regular consumption of whole oranges (but not squeezed and strained into juice).\na) Justify the concept of "empty calories" by contrasting the complete nutritional composition of both foods (micronutrients, fibre, and water).\nb) Predict and compare how the blood glucose curve will evolve after consuming the soft drink versus the two whole oranges, explaining the role of dietary fibre in the rate of absorption and in the sensation of satiety.

A fast food chain advertises: "Scientifically balanced meal: minced meat (proteins and fats), bread (carbohydrates), and a tomato slice with a lettuce leaf (vitamins and fiber)".\na) Critically contrast this advertisement with Harvard's "Healthy Eating Plate" model. Identify the qualitative and quantitative imbalances of the meal (actual proportion of vegetables, quality of the flours, and type of fats present).\nb) Modify the components of this meal to turn it into a truly balanced meal and write a scientific criterion that helps a consumer detect when food advertising uses half-truths.