Every season, just like fashion, we are presented with ‘new and improved’ weight loss programs. Many of these fall into the ‘fad diet’ category, without any scientific backing, and exit the scene just as quickly as they entered.

Perhaps you were quick to dismiss Intermittent Fasting (IF) diets as ‘just another fad’? But as it turns out, various forms of IF are gaining popularity by the day among health professionals and community members alike.

So what are IF diets?
As an overview – IF diets restrict intake on certain days of the week, or within certain hours of each day. This allows for greater ‘flexibility’ outside of restricted times (i.e. some treats within reason!). Traditional diets are more steady – they do not restrict, however, ‘flexibility’ is limited if you want to lose weight.

There are a few different forms of IF – here are three popular options:

The 5:2 Diet: 
The 5:2 diet was first brought to our attention by Dr Michael Mosely, from the UK, who also hosts the popular TV series ‘Trust me, I’m a Doctor’. It involves significantly restricting caloric intake for just two non-consecutive days a week (between 500 – 800 calories), whilst eating ‘normally’ for the other five days. Note – eating ‘normally’ does not mean going overboard, but there is some flexibility for treats.

Sample ‘fast’ day (500 calorie plan for women):

Breakfast 2 boiled eggs
1 tomato, sliced
140 calories
Lunch 2 cups of salad vegetables
1 tin of tuna in springwater
2 tbs low fat cottage cheese
Fat free dressing
160 calories
Dinner 100g chicken breast, grilled
2 cups of steamed low-carb vegetables
200 calories
Snack Low joule drinks (black tea, black coffee, herbal tea)
Diet Jelly – in moderation
0 calories

The 2-Day Diet: 
Similarly to the 5:2 diet, the 2-Day diet focuses on restriction for two days of the week. However, only carbohydrate intake is restricted on the two fasting days (<50g per day), not total calories. So that means – no breads, cereals, grains, starchy vegetables and most fruit. However, you can consume decent portions of healthy fat, lean protein and non-starchy vegetables to keep you full. For this version of IF, the two fasting days must be consecutive. The 2-Day Diet was developed and researched in the UK by Dr Michelle Harvie.

Sample ‘fast’ day (<50g carbohydrate):

Breakfast 150g Greek yoghurt (unflavoured)
1tsp each of pepitas and chia seeds, and 10 mixed nuts
½ cup strawberries
15g carbohydrates
MT 1 boiled egg
1 milky cup of tea
3g carbohydrates
Lunch 1 bowl of Hearty Chicken and Vegetable soup (recipe below!) 15g carbohydrates
AT 50g cottage cheese
1 medium carrot
6g carbohydrates
Dinner 120g baked salmon with soy sauce, chilli and ginger
Steamed Asian greens – 2 cups
7g carbohydrates
Supper 5 almonds and 1 square of 90% dark chocolate 3g carbohydrate

The 8:16 Diet:
This version of IF is a daily practice, unlike the two options above. It restricts food intake to an 8-hour window during the day (i.e. 11am – 7pm), and encourages fasting for the remaining 16 hours. Within the 8-hour window, participants are encouraged to make healthy food choices, with some flexibility for treats. During the 16 hour fast window, water and calorie free liquids (i.e. black coffee, tea, broths) are encouraged. Sometimes, your dietitian will allow low calorie vegetables as well!

Sample 8-hour diet plan:

Light Breakfast Protein smoothie – 30g protein powder with 1/2 cup frozen berries, 1/2 banana, 1tsp chia seeds, handful of spinach, milk of your choice. 11AM
Lunch Sandwich on Burgen Bread with smoked salmon, cream cheese, spinach, cucumber and grated carrot 2PM
Snack Sliced apple with 1tsp peanut butter 5pm
Dinner Thai beef stir fry with vegtables and basmati rice 7pm

So what are the benefits of IF?

  • IF diet can improve insulin sensitivity, reduce blood pressure and reduce LDL cholesterol – in addition to weight loss.
  • You may lose 0.5 – 1.0kg per week with IF, which is similar to restricting your current intake by 20-30% every day.
  • You may maintain a higher metabolic rate over the duration of your weight loss. This is because IF may prevent the body’s ‘adaptation’ to starvation, which lowers metabolic rate during traditional, continuous caloric restriction.
  • IF diets are relatively easy to follow, with clear guidelines for your ‘fast’ and ‘non-fast’ periods.
  • IF programs do not cut any food groups permanently, allowing you to enjoy variety, as well as meet all your nutrient requirements across the week.
  • IF programs typically allow greater flexibility for treats (during non-fasting periods), compared with traditional diets.
Who it suits: Those who find it hard to follow traditional calorie restricted diets, have tried unsuccessfully to lose weight in the past, and are looking for greater flexibility with treats (i.e. on weekends).

Are there any downsides to IF?

  • You may find it difficult to incorporate fasting into your routine, particularly if you have long, busy days.
  • You may feel light headed, fatigued, or have reduced capacity to perform normal work when fasting. This is particularly noteworthy for people with physically demanding jobs (i.e. labourers, tradesmen). Note – some people report that they feel more energized when fasting!
  • You may feel tempted to overeat on during non-fasting periods, and ‘undo’ all your good work This is especially true for people with a history of binge eating.
  • If you have diabetes and take insulin, you may be at risk of hypoglyaceia (unless you adjust your dosing).

Who it doesn’t suit: Those who get ‘hangry’, or cranky when they haven’t eaten, those who have a physically demanding job or high levels of daily activitys, and those with a history of binge eating.

Note – it is important that you chat with your GP and/or dietitian prior to commencing IF, especially if you have a health condition (i.e. diabetes).