In Australia, approximately two-thirds of adults and one-quarter of children were overweight or obese in 2018. Moreover, 60% of men and 66% of women had a waist circumference above the recommendations, putting them at a higher risk of disease. Overweight and obesity are a real problem in our society and are associated with a wide range of chronic diseases and also with premature death.
Diets and weight loss programs are numerous but do they really work? This month we will look in detail at intermittent fasting. Google records intermittent fasting as the trending dietary search term for 2019. Many celebrities swear by this diet and this is probably partly responsible for the popularity of this diet.
What is intermittent fasting?
Intermittent fasting is a periodic energy restriction as opposed to a continuous restriction of energy (calories/kilojoules). In other words, this diet is a cycle of eating and fasting. People following this diet restrict their intake sometimes, either based on the days of the weeks or based on the hours of the day. The two most popular types are the 5:2 and the 16:8 diets. On the 5:2 diet, people have a very low intake of approximately 500 kca/2,000 KJ for 2 non-consecutive days and eat normally for 5 days. Others choose to limit their eating window to only 8 hours and completely fast for the rest of the day (16 hours), this is the 16:8 diet. There are numerous variations of fasting, including alternate-day fasting or periodic fasting for religious reasons like Ramadan or lent.
Weight loss and other outcomes
Studies on the topic of weight loss and intermittent fasting are contradictory. Some studies found that intermittent fasting achieves a greater reduction in BMI (Cho, 2019) while other studies found a similar effect on weight loss between intermittent fasting and continuous energy restriction (Welton, 2020) (Cioffi, 2018). Intermittent fasting can have a positive impact on waist circumference, glycemic control or blood pressure but once again, the results are not always conclusive and not proven over 6 months.
There are usually no serious side effects to intermittent fasting but some people report reduced energy level, hunger, constipation, lack of concentration, mood swings, headaches, dizziness, nausea or sleep disturbance.
A recent meta-analysis (a type of study compiling results from several similar studies) showed a greater reduction of weight and BMI for participants doing alternate-day fasting (Cui, 2020). Alternate-day fasting is also known as the 4:3 diet where every other day is restricted to approximately 500 kca/2,000 KJ. This type of fasting also showed a reduction of total cholesterol, LDL-cholesterol, triglycerides, fat mass and blood pressure when compared to control groups. The change in HDL-cholesterol and fasting blood sugar was similar for the alternate-day fasting and the control group.
What about religious fasting
Studies comparing Ramadan and non-Ramadan fasting, showed that both types are effective on fat mass and body weight losses. However, fat mass loss is greater with non-Ramadan intermittent fasting and when combined with physical activity, induced a higher decrease in BMI (Correia, 2021).
Is it for me?
The issue with intermittent fasting is the reliance on external cues to guide the food intake. People doing intermittent fasting
restrict their eating pattern based on time instead of focusing on their internal cues. Will intermittent fasting work for you? It might or it might not, you can’t tell until you try. There are no severe side effects reported so it is generally considered safe to try. At the end of the day, weight loss is mathematical. Energy expenses need to be greater than the intake to induce a reduction of weight.
Maintaining weight loss
Studies show a similar or greater weight loss for intermittent fasting when compared to other types of energy restriction. The difficulty remains to maintain the weight loss over time, with the maximum weight loss being achieved around six to 12 months. You should aim at changing the three lifestyle areas related to overweight and obesity as this is more effective for weight maintenance than focusing on only one component. The
three lifestyle focus are:
2. Physical activity
3. Psychological approaches to behavioral change
Book your first appointment with me and discuss how I can help you stay healthy and achieve your goals!
Tracy L’Allier Ebacher
Accredited Practising Dietitian