SARAH DI LORENZO: Diet fad intermittent fasting isn’t the magic weight loss fix it’s made out to be

As a Clinical Nutritionist, I’ve had a range of patients — mostly motivated by weight loss — come into my clinic telling me how they’ve tried intermittent fasting. Most have done the 16:8 method, usually by skipping breakfast and eating between 12 pm and 8 pm. My first response is to ask what success they’ve had with it. Most have had none.

Intermittent fasting (IF) has gained attention not only for its potential weight loss benefits but also for its possible impact on health more broadly. It’s an umbrella term for different ways of time-restricting eating. The most popular, as mentioned, is the 16:8, where you eat within an eight-hour window each day.

There’s also alternate-day fasting, where you eat normally one day and follow a very low-calorie plan the next. Then there’s the 5:2 diet — where five days of the week are normal eating, and two days are reduced to around 500 calories.

The 16:8 is the most common because it’s simple — most people just skip breakfast. It tends to fit into people’s lifestyles and doesn’t involve many strict rules.

While some report weight loss at first, in my experience, most people overeat during the eating window and end up seeing little to no result.

The 5:2 diet is where I’ve seen the most success. It’s flexible and focuses only on two low-calorie days. However, it can be tricky around social events, so I always encourage patients to plan their low days when they know they’ll have control over their meals.

Alternate-day fasting can be hard to sustain. People often report low energy on the fasting days. I sometimes use it as a short-term strategy to break through a weight loss plateau, but it’s not sustainable long term.

The reasons people try intermittent fasting vary. Weight loss is a big one — due to reduced calorie intake — but also because of the potential for metabolic benefits. There are studies showing improvements in insulin sensitivity, blood sugar levels, and lipid profiles.

Some research suggests intermittent fasting may support heart health — lowering inflammation, cholesterol and blood pressure when done properly. There are also early studies (mostly in animals) pointing to benefits for brain function, including the growth of new neurons and protection against damage — but more research is needed before we can draw strong conclusions for humans.

A particularly popular aspect of intermittent fasting is its link to cellular repair and longevity. Fasting triggers autophagy — a process where the body clears out damaged cells and regenerates new ones — potentially reducing the risk of disease and supporting healthy ageing.

That said, there are risks and important things to consider. Long fasting periods can lead to nutrient deficiencies, and for some, it can become a form of disordered eating. It’s not suitable for everyone — including pregnant or breastfeeding women, people on certain medications, and children or teenagers who are still growing.

People should also be aware of side effects that can affect daily life — things like moodiness, irritability, headaches, hunger, low energy, difficulty concentrating and reduced productivity.

While intermittent fasting can offer health benefits, it’s far from a one-size-fits-all approach. In fact, the best success I’ve seen has been with people following low-calorie days like those in the 5:2 diet.

Statistics show that while around 70 per cent of people lose weight in the first three months, only 25 per cent continue with intermittent fasting after six months. The ones who succeed tend to be structured, consistent, include protein in their meals and stick to the plan with discipline.

Success with intermittent fasting depends on the individual’s goals, mindset and commitment. For most, it’s not what it’s cracked up to be. Eating regular, portion-controlled meals — without skipping — is still the key to long-term success when it comes to health and wellness. If you’re considering fasting, my advice is to focus on lowering calorie intake without skipping meals.

And always consider speaking to a qualified health professional before starting.