Fad diets are easy to spot – they always sound too good to be true! They over promise results and more often than not leave you feeling worse than when you started. Whether it’s keto, juice cleansing or any other random or obscure approach, they all have one factor in common - they use extreme patterns of eating to create weight loss.

More specifically, a fad diet is a way of eating that results in unsafe, rapid weight loss that isn’t backed by sound scientific evidence. Often these claims are just plucked out of thin air or use unreliable studies as their basis.

What is a diet?

In an ideal world, the word ‘diet’ is used to describe the food and drink you consume. Unfortunately, over the years, this meaning has been lost. Instead, when you hear the word diet, you probably just think of reducing or restricting food with the aim of losing weight.

How do diets work?

While factors such as genetics, sleep and stress can influence weight, a considerable element of weight management is energy balance - effectively the balance between energy in (i.e. calories consumed) and energy out (e.g. exercise or movement). Weight gain occurs when there's more energy being consumed than used or expended – a positive energy balance. Weight loss is the result of the opposite, where there’s more energy being expended than consumed – a negative energy balance. When energy consumed is the same as energy expended, weight is maintained.

A fad diet simply creates a negative energy balance, also known as an energy deficit, which is often extreme and dangerous.

How much weight is safe to lose?

Registered health professionals recommend safe weight loss as 0.5-1Kg per week. This guidance is typically overlooked by fad diets as it’s simply not glamorous enough to sell their approach. Fad diets would far rather promise you a much more drastic, albeit far less safe and unsustainable weight loss of 3-4Kg per week.

To achieve such rapid weight loss, a significant energy deficit is needed, which severely restricts food and nutrient intake. As a result, you’re more likely to miss out on key macronutrients such as fibre, as well as essential vitamins and minerals. Subsequently, you’re at greater risk of illness and you’ll most likely start feeling fatigued and irritable.

How do I know I’m not just losing water?

Body composition can be broken down into three categories: fat mass, fat free mass (think muscle, bone and tissue) and water. When looking at healthy weight loss, it’s fat mass you’re looking to lose, but this will be slow and steady. The drastic losses promised by fad diets are typically water, not fat mass, so not the good news stories they claim to be.

Take a fad diet such as Keto, which cuts out carbohydrates. Carbohydrates are stored in the body as glycogen (a store of carbohydrates), alongside water. This water is used to break down the glycogen when the body needs energy. If carbohydrates aren’t being consumed, glycogen isn’t formed, meaning water isn’t being stored. As a result, a reduction in weight may occur. Of course, if you’re eating within an energy deficit alongside, you will experience reductions in fat mass – though you’ll likely also decrease muscle mass too.

What can you do instead?

Instead of jumping from one fad diet to the next, the key to sustainable and lifelong weight management is sustainable lifestyle changes. These don’t need to be drastic. Even the smallest of changes in diet and lifestyle can deliver big results.

Why not start by looking at your fruit and vegetable intake? If you’re not getting your five-a-day, perhaps start on this, as fruits and vegetables are fibre packed, helping you feel full for longer. Or perhaps think about moving more. Our lifestyle Facebook group has our Run, Walk, Run programme to help the transition from walking to running, or if you’re not ready to run then look towards that 10K daily step target. Movement matters and can make a big difference.

Harley Street at Home is proud to run the 12 week Back to Basics Menopause Lifestyle and Weight Management programme, which rejects fad diet behaviours. Instead, the programme focuses on realistic and sustainable lifestyle changes that will leave you thriving, and as a result you’ll start to see a change in your weight. You’ll never eye up a fad diet again!

For more on fad diets, join Lucy Jones (ANutr) in her How to Spot a Fad Diet workshop on Tuesday 7th June at 7pm.

This blog post was written by our nutritionist Lucy Jones (ANutr). You can find Lucy on Instagram at @lucy.nutritionn.