Healthy eating habits/Fad Diets: What are they really doing to you?

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The following article provides education material on two particular fad diets; the Dukan diet and the 5:2 diet. It explains what happens in the body when dieting and provides tips for taking a healthier approach to weight loss. This guide is targeted towards females in their twenties.

Fad Diets

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A fad diet is a weight loss diet which cuts out one or more food groups or recommends eating a particular food at the expense of others. [1] It usually promises significant weight loss in a short amount of time and is often not scientifically proven. [1]

Fad diets are often difficult to maintain because:

  • They are usually very low in calories or cut out nutrients that our body needs to function. [1] This causes us to crave particular foods that the diet tells us we can’t have.
  • They cause us to lose water and muscle weight rather than fat. [1] This makes us feel like we are losing lots of weight but it will actually slow our metabolism and make it easier to gain fat once the diet is over.
  • They teach us short term behaviours that are not practical in the long term. [1] This causes us to revert back to our old habits once the diet is over.

Dukan Diet

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What it involves

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A range of protein-rich foods

Involves 4 phases:

1. Attack phase

  • For rapid weight loss (2-3kg in 2-10 days)
  • Can eat lean protein foods only (as much as desired) (e.g. beef, chicken, fish, eggs, soy foods)
  • Must have 1 ½ tablespoons of oat bran and 1 ½ litres of water per day

2. Cruise phase

  • For gradual weight loss (1kg per week)
  • Can eat unlimited amounts of protein and non-starchy vegetables (e.g. spinach, lettuce, green beans)

3. Consolidation phase

  • To prevent weight gain
  • Can eat unlimited amounts of protein and vegetables plus 1 low-sugar fruit (e.g. citrus fruit, berries), 1 slice cheese and 2 slices wholegrain bread per day
  • Can have 1-2 starchy foods (e.g. pasta, potatoes, rice) and 1-2 celebration meals per week

4. Stabilisation phase

  • For long-term weight maintenance
  • Can eat everything
  • Must follow 4 rules:

(1) Have one all-protein day per week
(2) Consume 3 tablespoons oat bran per day
(3) Go for a 20 minute walk every day
(4) Always use stairs; never take the escalator or elevator

Side effects

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  • Tired [2]
  • Constipation [2]
  • Vitamin and mineral deficiency [2]
  • Weak bones [2]
  • Kidney problems [2]

5:2 Diet

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What it involves

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Involves eating normally for 5 days of the week and fasting for 2 days of the week. This is called intermittent fasting. On fasting days, one quarter of normal intake can be eaten.

2000kJ worth of food: wholemeal toast with butter and jam and a grilled fish fillet with salad

For women this is about 2000kJ (500cal) which looks like:
Breakfast: 2 slices wholemeal toast with butter and jam
Dinner: 1 grilled fish fillet with salad

The diet is based on the idea that if less energy (kJ) is consumed over the entire week, weight loss will occur. People are expected to lose ½ kg per week but this depends on how much is eaten on non-fasting days. If people tend to binge eat because they know that a fasting day is coming up, they may not lose much weight at all.

A flowchart showing what happens in the body when on a fad diet

Side effects

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  • Low in energy [3]
  • Poor concentration [3]
  • Bad mood [3]
  • Compromised social life [3]

What Happens in the Body when on a Fad Diet

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After eating carbohydrates, those that are not used in the body are stored in a form called glycogen. [4] When carbohydrates have not been eaten for a while, for example on a fad diet, the body uses its glycogen stores to provide energy and keep the brain functioning. [4] Over time, these stores run out and the body turns to protein and fat for energy. [4] This means muscle loss occurs because that is where protein is stored. Muscle uses more energy to function than fat so less energy is burned as more muscle is lost. [4] This is called decreasing metabolism. Having a low metabolism makes it easier to gain weight once the diet is over because less energy is being used up. [4]

3 Top Tips for Healthy Eating and Weight Loss

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1. Eat something from each food group every day

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It can be very hard to eat the recommended amount of food from each food group every day. By ticking off food groups as you eat them, you can make sure you are giving your body a bit of each nutrient it needs to function.

For example:

Meal Food Food group
Breakfast Cereal




Lunch Wholemeal bread sandwich




Dinner Grilled chicken breast

Potato wedges
Roasted pumpkin
Green bean salad



2. Eat a source of grains at every meal

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Eating a source of grains at every meal will make sure your body has enough energy to sustain it throughout the day and will stop you from eating everything in sight when you have deprived your body of its favourite source of energy.

Bread and grains

For example:

Meal Food Grain source
Breakfast Muesli on yoghurt Muesli
Lunch Vita Weat crackers with salad Vita Weat crackers
Dinner Brown rice side dish with chicken and vegetables Brown rice

3. Exercise for at least 30 minutes every day

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Exercising can be as simple as walking around your block or dancing around your bedroom. If you are more motivated, you can go cycling, swimming, jogging or play a team sport.


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  1. a b c d e Dietitians Association of Australia (DAA). (2014). Fad Diets. Retrieved from
  2. a b c d e Fad Diets. (2000). Nursing Management, p.18-19.
  3. a b c d Collier, R. (2013). Intermittent fasting: the next big weight loss fad. Canadian Medical Association Journal, 185(8), p. E321-E322. doi: 1503/cmaj.109-4437
  4. a b c d e Bilsborough, S. (2007). Finding Facts in Fad Diets. Issues, 84, p. 28-31. Retrieved from