The diet on everyone's lips (and hips) this year is the 5:2 diet.
Hailed by nutritionists and celebrities galore, the way it works is simple: dieters restrict calorie intake for two days (to 500 calories for women and 600 for men) and eat what they like for the remainder of the week. And the weight just falls off.
The diet, which was first featured in a BBC Two Horizon documentary by health journalist Dr Michael Mosley, has raised concerns with people questioning the health implications of fasting.
How can fasting on just two days per week help dieters lose weight?
The benefits are related to the changes which take place in the body as a result of fasting, rather than being linked to the reduction in calories.
These short fasts lead the body into a metabolic state which triggers repair and recovery at a cellular level. This influences hormones, and allows the digestive system and related organs to rest. This is especially true with the pancreas (the gland which produces insulin in response to carbohydrates and sugar). The body becomes more sensitive to insulin, which is one of the most important aspects of weight loss.
Additionally through regular, short-term fasts, individuals have a better sense of control on 'non-fast days', choosing foods that are more healthy and rarely eating out of boredom.
Is losing weight quickly unhealthy?
The 5:2 fast diet is different because the calorie restriction only happens on 2 days a week. On the other 5 days of the week, there is no diet, no calorie counting and normal eating. It isn't a short term solution but rather a long term way of eating.
The fasting also brings about improvements to a range of markers associated with improved health, such as cholesterol. So it is a healthy way of eating.
Find out more on the 5:2 diet here
What could be the side effects of going on the diet?
There are more positive side effects than negative.
The first couple of fast days can be a challenge but eventually individuals enjoy fast days, feeling lighter, more alert, more energetic and awake.
It is essential that the 5:2 Fast diet is approached sensibly. The non-fast days should not be calorie restricted to ensure that over the week, sufficient calories are still consumed and it is vitally important to consume the right nutrients on a daily basis.
Here are some exclusive 5:2 recipes to try out for yourself
224 calories Serves 1 Preparation time: 5 minutes Cook time: about 8 minutes ½ tsp extra-virgin olive oil (14 cals) 1 garlic clove, peeled and finely chopped (3 cals) 1 tbsp tomato purée (paste) (30 cals) 4 anchovy fillets, drained (24 cals) Heat the olive oil gently in a small frying pan (skillet), add the garlic and fry for 1–2 minutes until just starting to go brown. Stir in the tomato purée (paste) and 2 tablespoons water, then fry gently for another 4–5 minutes. Spread the tomato sauce over a warm flatbread and arrange the anchovies over the top. Slice into quarters and eat straight away. Recipe courtesy of The 5:2 Bikini Diet
185 calories Make sure to score a line round the middle of the apple before filling, otherwise the apple may split during cooking. Serves 1 Preparation time: 10 minutes Cook time: 35–40 minutes 1 large Bramley (cooking) apple (54 cal) 1 tsp (5g/1/8oz) butter (37 cals) 1 tsp (5g) flaked (slivered) almonds (32 cals) 2 tsp (10g/1/3oz) soft dark brown sugar (36 cals) ½ tsp ground mixed spice 10g (1 heaping tsp) raisins (27 cals) grated zest of ½ orange Preheat the oven to 190°C/fan 170°C/375°F/Gas mark 5. Use an apple corer to remove the core from the apple, then score round the middle of the apple with a sharp knife, cutting to a depth of about 5mm (1/4in) all round. Place the apple in a small serving dish. Mix the rest of the ingredients together in a small bowl and use to stuff the filling into the centre, rubbing a little round the apple as well. If there is any filling left over, pile it on the top. Cook in the oven for 35–40 minutes until golden and soft. Recipe courtesy of The 5:2 Bikini Diet
244 calories This chicken satay can be either barbecued or grilled (broiled). They taste delicious served on a bed of spinach with some lime juice squeezed over, adding on the appropriate calories, if you are on a fast day. If using wooden skewers, make sure they are soaked in a bowl of water for at least 30 minutes before using to prevent them burning during cooking. Serves 2 Preparation time: 10 minutes, plus 3–4 hours marinating Cook time: 10 minutes 250g (9oz) skinless chicken breast, cut into cubes, about 2.5cm (1in) square (265 cals) 1 shallot, peeled and diced (5 cals) 1 garlic clove, peeled and crushed (3 cals) 2 tsp curry powder 1 level tbsp peanut butter (182 cals) 1 tsp runny honey (23 cals) 2 tbsp soy sauce (9 cals) To make the marinade, mix the shallot, garlic, curry powder, peanut butter, honey and soy sauce together in a bowl. Add the chicken and toss until the chicken is coated all over in the marinade. Leave to marinade in the refrigerator for 3–4 hours. Preheat the grill (broiler) to medium or light the barbecue. Thread the chicken cubes onto 2–4 skewers, leaving room between the chicken pieces to allow them to cook thoroughly. Grill (broil) for about 10 minutes, turning regularly, until cooked through. Serve immediately. Recipe courtesy of The 5:2 Bikini Diet
146 calories A great fat-free dessert, it is made without the use of an ice-cream machine. Remember to take the frozen yogurt out of the freezer 10 minutes before serving to allow it to soften slightly. Feel free to experiment with other fruits using a similar method, or try adding a few drops of vanilla extract to make vanilla frozen yogurt. Serves 6 Preparation time: 10 minutes, plus 3–4 hours freezing 200g (scant 12/3 cups) raspberries (50 cals) ½ x 405g (14oz) can light condensed milk (541 cals) 500g (generous 2 cups) pot 0% fat Greek yogurt (285 cals) Roughly chop half the raspberries and set aside. Place the remaining raspberries in a food processor and whiz to a smooth purée. Alternatively, purée the raspberries with a fork. Place the puréed raspberries in a large bowl and stir in the condensed milk and Greek yogurt until well everything is mixed, then fold in the remaining chopped raspberries. Transfer the mixture to a freezerproof container and freeze until solid. Recipe courtesy of The 5:2 Bikini Diet
215 calories Serves 1 Preparation time: 5 minutes Cook time: 8 minutes, plus 10 minutes cooling 2 vine ripened tomatoes, sliced (26 cals) ½ red (bell) pepper, deseeded and cut into strips (25 cals) 50g (13/4oz) light halloumi, drained and sliced into thin squares (122 cals) 75g (3oz) Italian mixed salad leaves (greens) (10 cals) For the marinade ½ garlic clove, peeled and crushed (2 cals) juice of 1 lime (3 cals) 1 tsp chopped fresh parsley ½ tsp chilli flakes (red pepper flakes) freshly ground black pepper 1 tsp extra-virgin olive oil (27 cals) To make the marinade, combine the garlic, lime juice, parsley, chilli flakes (red pepper flakes), pepper, 1 tablespoon water and the olive oil in a wide bowl. Add the sliced tomatoes to the marinade. Heat a large frying pan (skillet) and dry-fry the red (bell) pepper strips for about 5 minutes until slightly blackened, then put them with the tomatoes in the marinade. Fry the halloumi slices in the same pan until golden on both sides, they will only take a minute in a hot pan. When they are cooked add them to the marinade and turn until the halloumi is coated all over. Leave the halloumi to cool for about 10 minutes. Arrange the salad leaves (greens) on a wide serving plate and put the halloumi, pepper strips and tomatoes on top. Drizzle over the remaining marinade and serve. Recipe courtesy of The 5:2 Bikini Diet