Year 9 Health & PE · Health and Physical Education · 18m read

Nutrition and Body Image

Ever noticed how nutrition advice seems to completely contradict itself from one week to the next? Understanding how food actually affects your body—and your relationship with it—helps you see through confusing marketing and make choices that work for *you*. This isn't about following strict rules; it's about connecting what you eat to how you feel and look, and recognizing that health looks different for everyone.

Learning objective: Analyse the relationship between nutrition, body image and health outcomes.

By the end of this lesson you can:

• I can explain the principles of evidence-based nutrition.
• I can describe how media and culture influence body image.
• I can evaluate strategies to support positive body image.

Body image is a mirror that can be bent. Media, comments and comparison can bend the mirror. Focusing on health and function straightens it.

Nutrition, body image and wellbeing

EVIDENCE-BASED NUTRITION:
• MACRONUTRIENTS: carbohydrates (energy), proteins (building/repair), fats (brain, hormones).
• MICRONUTRIENTS: vitamins and minerals — essential in small amounts.
• AUSTRALIAN DIETARY GUIDELINES: 5 food groups, water, minimise processed food/alcohol.

ADOLESCENT NUTRITION NEEDS:
• Higher calcium (bone building), iron (especially for girls), protein (growth), zinc.
• Breakfast: associated with better concentration and academic performance.
• Hydration: dehydration affects cognition and mood.

FOOD ENVIRONMENT:
• "Obesogenic environment": designed to make unhealthy choices easy and cheap.
• Ultra-processed foods: engineered to be addictive; high sugar, salt, fat.
• Food marketing targeted at youth: builds brand loyalty, associates unhealthy food with fun.

BODY IMAGE:
• How we SEE, FEEL and THINK about our bodies.
• POSITIVE body image: acceptance and appreciation of your body.
• NEGATIVE body image: shame, dissatisfaction — risk factor for eating disorders.

INFLUENCES ON BODY IMAGE:
• MEDIA: airbrushed images, unrealistic standards.
• SOCIAL MEDIA: comparison with "ideal" bodies (Instagram effect).
• PEERS: comments about bodies, diet culture.
• FAMILY: messages about food and weight received in childhood.

MEDIA LITERACY FOR BODY IMAGE:
• Recognise digital manipulation (filters, airbrushing).
• Follow accounts promoting body diversity and health at every size (HAES).
• Challenge "diet culture" messages.

EATING DISORDERS:
• Serious mental health conditions; not about food — about control, coping, trauma.
• Early intervention is critical — seek professional help.

AARI TIP: Ask Aari about the evidence on "diet culture" and its impact on mental health.

Nutrition fundamentals

• Variety: No single food is "good" or "bad" — variety and balance matter.
• Hunger cues: Intuitive eating — eat when hungry, stop when full.
• Health at every size: Body size alone does not determine health status.

Quick reference

| Topic | Key point |
|---|---|
| Five food groups | Variety |
| Fad diets | Often unsustainable |
| Positive body image | Respect your body |
| Eating disorders | Seek help early (Butterfly Foundation) |
| Media literacy | Spot editing and filters |

Worked example (Medium)

Critically evaluate a social media fitness influencer's advice: "Cut all carbs to lose weight fast."

1. Source evaluation. Is this person a qualified dietitian or nutritionist? Social media credentials ≠ scientific expertise.
2. Evidence check. Low-carb diets can produce short-term weight loss but are not superior to other approaches long-term (research shows). For adolescents, carbohydrates are the brain's primary fuel.
3. Harm potential. Extreme carb restriction for teens can impair brain function, athletic performance, and in vulnerable individuals, trigger disordered eating.
4. Bigger picture. Focus on a "fast" result ignores sustainable healthy habits. "Diet culture" is associated with weight cycling and worse long-term health outcomes than stable, nourishing eating.

Answer: This advice is unsupported by evidence, potentially harmful for teens, and reflects diet culture rather than public health science.

Common mistakes

• Saying carbohydrates are "bad" or should be avoided Carbohydrates are the brain's primary fuel and the body's preferred energy source. Low-carb diets can impair cognitive function and athletic performance in adolescents Fix: Distinguish between refined carbohydrates (white bread, sugary drinks — limit) and complex carbohydrates (wholegrains, legumes, fruit — prioritise)
• Equating thinness with health Body size alone does not determine health. Underweight individuals can have nutrient deficiencies, hormonal disruption and weakened immune systems Fix: Use "Health At Every Size" (HAES) framework: health behaviours (varied diet, movement, adequate sleep) matter more than weight or appearance
• Treating eating disorders as "just a diet" or a choice Eating disorders are serious mental health conditions with the highest mortality rate of any psychiatric illness. They are not about food — they involve control, trauma, anxiety and complex psychological factors Fix: Eating disorders require professional treatment. Recognise warning signs and encourage immediate professional help rather than trying to address them informally

Worked example (Hard)

A 15-year-old athlete has been severely restricting food intake to "make weight" for their sport, and appears to be losing muscle mass and energy. Apply the Female Athlete Triad (or Relative Energy Deficiency in Sport — RED-S) framework to analyse this situation.

1. Identify the issue — RED-S. Relative Energy Deficiency in Sport (RED-S) occurs when energy intake is chronically insufficient to support training demands. Originally termed the "Female Athlete Triad" (low energy availability, menstrual dysfunction, low bone density), RED-S is now recognised in athletes of all genders.
2. Low energy availability. The athlete is consuming fewer calories than expended in training — the body responds by lowering metabolic rate, reducing hormones, breaking down muscle. Performance paradox: trying to improve by restricting food actually decreases strength, endurance and reaction time.
3. Physiological consequences. Hormonal disruption (testosterone/oestrogen). Reduced bone density — stress fractures. Impaired immune function — recurrent illness. Cardiac effects. Growth stunting in adolescents whose bones are still developing. Cognitive impairment — brain function depends on adequate glucose.
4. Psychological dimension. Weight-focused sport culture, coaches emphasising appearance over performance, and comparison with teammates can create or reinforce disordered eating. This requires sensitive, non-stigmatising support from parents, coaches and health professionals.
5. Appropriate response. Immediate referral to a sports dietitian and GP. Review of training load vs nutrition intake. Cultural change in the sporting environment away from weight focus. Ensure the athlete is not judged or shamed — eating disorder risk increases with stigmatising responses.

Answer: RED-S illustrates that restricting nutrition can have paradoxical, serious consequences for athletic performance AND health. Adequate nutrition is performance nutrition.

Practice questions

1. Which macronutrient is the brain's primary fuel source?

   1. Protein
   2. Fat
   3. Carbohydrates
   4. Fibre

   (1 marks)

2. Explain how social media can negatively impact adolescent body image.

   (3 marks)

3. The Australian Dietary Guidelines recommend:

   1. Avoiding all fats.
   2. Eating from 5 food groups with variety and balance.
   3. Following a low-carbohydrate diet for optimal health.
   4. Eating 3 large meals with no snacks.

   (1 marks)

4. Evaluate the "obesity epidemic" narrative. What does the evidence say about the relationship between body weight and health? Consider the HAES (Health at Every Size) perspective.

   (4 marks)

5. Identify two nutritional needs that are particularly important during adolescence and explain why.

   (2 marks)

Deeper Understanding: The Science of Gut Health and the Microbiome

One of the most exciting areas of nutritional science in the past two decades is the gut microbiome — the complex ecosystem of approximately 100 trillion bacteria, fungi and other microorganisms living in the human digestive tract. Research has revealed that the gut microbiome influences not just digestion but immune function, mental health (the "gut-brain axis"), inflammation, metabolism and even behaviour.

Diet profoundly shapes microbiome composition. High-fibre diets (vegetables, legumes, wholegrains) feed beneficial bacteria that produce short-chain fatty acids (SCFAs) — compounds that reduce inflammation, strengthen the gut lining, and may protect against metabolic disease. Ultra-processed foods, conversely, are associated with reduced microbiome diversity, which correlates with higher rates of inflammatory diseases, depression and metabolic syndrome.

The gut-brain connection runs through the vagus nerve and various neurochemical pathways. Approximately 90% of the body's serotonin (a key mood-regulating neurotransmitter) is produced in the gut — not the brain. This means gut health directly affects mood and mental health, explaining why dietary patterns are increasingly linked to depression and anxiety risk. Australian researchers at Deakin University's Food and Mood Centre have published landmark studies showing dietary interventions (moving to Mediterranean-style diets) can significantly reduce depression symptoms in clinical trials.

For adolescents, this research underscores the importance of fibre-rich, varied diets during a period when both the microbiome and the brain are still developing. The habits formed in adolescence shape microbiome composition that may persist into adulthood.

Summary

• Macronutrients: carbohydrates (energy/brain fuel), protein (building/repair), fats (brain, hormones).
• Australian Dietary Guidelines: variety from 5 food groups, water, limit processed foods.
• Adolescent priority nutrients: calcium (bone building), iron (especially girls), protein, zinc.
• Body image is influenced by media, social media, peers and family — media literacy is protective.
• Eating disorders are serious mental health conditions requiring professional treatment.
• HAES: health-promoting behaviours benefit everyone regardless of body size.