Are there benefits of the 5:2 diet and is it healthy?
Intermittent fasting is a method for achieving weight loss that involves condensing your food intake into time restricted periods. The 5:2 diet is a type of intermittent fasting, whereby you fast (eat very little) for 2 days and eat normally for 5. The 2 fasting days should not be consecutive, and food intake is recommended to be restricted to 500-600 calories on these days.
The science behind the 5:2 diet and the benefits
The 5:2 diet gained popularity after scientific studies showed it could reduce the risk of developing type 2 diabetes, heart disease and some cancers. These studies were however done with animals, and there are yet to be good quality human studies showing the same results.
One large study that was done with humans (1) showed the 5:2 diet resulted in weight and fat loss, however the results were no different to using any other calorie controlled weight loss plan.
Pros of the 5:2 diet
• The flexibility of the 5:2 diet is a key draw card. You can choose which days are your fasting days, and how your make up your calories on these days.
• On normal days, nothing is technically off limits and there is no need to count calories.
• It is simple to do and cost effective, with no special foods or shakes required.
• Studies that have researched the 5:2 diet with humans found that the dropout rate of participants was relatively low, suggesting it may be easier to stick to than other diets.
Cons of the 5 2 diet
• Food needs to be planned carefully, especially on fasting days, to make sure you are getting adequate nutrition and hydration.
• Many people find they feel fatigued, get headaches or are irritable on fasting days. It may be more difficult to concentrate and exercise on these days.
• The calorie limit on fasting days is very small, and people may feel hungry and deprived on these days. Consequently there is a risk of overeating on non-fasting days, which could result in no weight being lost on the diet.
• As with any diet, it only works if you stick to it. You need to consider if fasting for 2 days per week fits your lifestyle long-term.
What foods you can eat on the 5:2 diet
There are no strict rule as to what to eat on the fasting days of the 5:2 diet, but calorie intake should be around 500 per day for females and 600 per day for males. Careful consideration needs to be given to what you eat on those days. Foods should be high in micronutrients (vitamins and minerals), contain some protein, and fibre. Examples include:
- Natural yoghurt with berries - Vegetable soup - Salads or vegetables with a small serve of lean meat or fish - Eggs - Drinks should be low calorie including water, sparkling water and tea or coffee.
On non-fasting days, you still need to eat a healthy diet, including foods from all food groups. Choose wholegrain bread and cereals, plenty of vegetables, leans meats and fish, legumes, fruit and dairy foods. Water should be the main drink.
Risks of the 5:2 diet
The 5:2 diet does not suit everyone and there may be medical risks associated with it. If you have any medical condition that is affected by what you eat, you should consult with a doctor before starting the 5:2 diet. Pregnant women, children and those who take medication for diabetes should not follow the 5:2 diet. As with any restrictive diet, there is the risk of developing a poor relationship with food.
When you should stop the 5:2 diet
If you feel unwell, for example with severe nausea, bad headaches or dizziness, you should stop the 5:2 diet. If you feel your relationship with food is being negatively affected, if you develop high levels of anxiety in relation to food, this is another sign to stop the diet.
Prepared by Kara Vogt – Accredited Practicing Dietitian
Trepanowski J F et al. Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial. JAMA Intern Med . 2017 Jul 1;177(7):930-938.