The diet that this ultra-fit pharmacist swears by

With single digit body fat and washboard abs sharp enough to cut the thick summer air, many would assume that Holly Louise's diet would have more rules than a North Korean prison.

Perhaps something like "no carbs after dinner" or more realistically, "no carbs at all"?

Not so, says the personal trainer, pharmacist and Body Science expert – her body was built with just one thing in mind: flexibility.

The eating style she's referring to – as the name implies – is called "flexible dieting", and some of the fittest people in the country have been eating this way for years to stay lean all year round.

Unlike literally any other diet on Earth, flexible dieting does not contain a single rule – you can more or less eat whatever you like, at whatever time you like. It sounds absurd, but involves more than simply stuffing your face with whatever's at hand.

As Louise explains, the beauty of flexible dieting is that you never feel like you're restricting yourself.

"Firstly, flexible dieting is not a diet – it is an approach to nutrition," Louise tells Coach.

"It involves meeting daily targets of macronutrients (protein, carbohydrate and fat) that have been calculated specifically for you in order to reach a specific body composition goal."

Flexible dieting: the basics

Okay, so you want to get leaner without totally cutting out foods like ice-cream and the occasional slice of pizza. Sound impossible? It isn't, but as Louise explains you do still have eat healthy food most of the time.

"The main focus is on reaching your macronutrient targets as the driver of your results, with food selection left up to you," says Louise.

"With this being said, at least 80 percent of the foods you eat on a daily basis should be composed of nutritious whole foods, while 20 percent can be used for more processed foods."

So every day that you eat, you'll have a rough idea of how many grams of protein, fats and carbohydrates you're consuming, and this in itself takes care of the calories.

"Rather than typical calorie counting (for example, a goal of eating 2000 calories per day), flexible dieters track macronutrients," explains Louise.

"The three main macronutrients – protein, fat, and carbohydrate, all have a caloric value per gram: protein has four calories per gram, carbohydrate has four calories per gram, and fat has nine calories per gram.

"Therefore by tracking ‘macros’ you also track calories by default – it is essentially just taking it a step further."

To put that into some kind of context, Louise says the day of someone wanting to eating 2000 calories would look a little like this:

• Protein = 143g

• Carbohydrate = 213g

• Fat = 64g

Of course, Louise is quick to point that the old rules of “energy in, energy out” still apply – it's just that counting macros gives you more flexibility than constantly chowing down on boiled chicken and broccoli.

"Remember, to lose fat you must consume less calories than you burn (a calorie deficit), to remain the same weight your calories in and calories out should remain the same, and to gain weight you must consume more calories than you burn (a calorie surplus)," explains Louise.

Counting macros is way easier than you think

If you're feeling totally overwhelmed with the idea of counting macros, take a deep breath and relax: because there's an app that will totally do that for you.

"The easiest way to organise, plan and track your food intake is via MyFitnessPal, which is available as a smartphone application for added convenience," says Louise.

"This allows you to keep an accurate food diary which you can alter at any time of the day. It is imperative to invest in a food scale to weigh out the portions of food you have selected to eat and enter them accordingly."

Okay, so you've weighed your food and punched everything into the app, and now you're good to go for most meals when you're at work. But what about when you eat out, forget your lunch, or (gasp) go to a party?

Easy, says Louise – after flexible dieting for a while, you'll become such a whiz at calculating everything that you can fit almost anything into your macros, and not worry about it.

"Once you have been tracking for a while you become familiar with portion sizes, which allows you to then begin guesstimating without weighing your foods," says Louise.

"This becomes very useful when eating out at restaurants or social occasions!"

It's pretty much the easiest 'diet' to stick to

Let's face it, as soon as you say to yourself "I'm on diet", the cravings begin: one minute you're nibbling on a single Oreo and 10 minutes later you've eaten an entire packet in a kind of sugar-zombie-induced stupor.

Luckily, because flexible dieting has room for a little treat every now again (usually that you'll fit into your carbohydrate macros), those cravings just aren’t as intense.

"Experience has also shown that restrictive diets which significantly reduce calories and eliminate food groups are not sustainable and lead to binge eating, cheating, and yo-yo dieting," explains Louise.

"This in turn creates feelings of guilt, generates self-punishment and negative emotions, resulting in a very unhealthy relationship with food and body image."

As Louise points out, flexible dieting manages to achieve the ideal fitness nirvana we all strive for: balance.

"Life is about balance and enjoyment, therefore, eating a sustainable diet is more likely to lead to success," says Louise.

RELATED: How to stick to a diet for good

It works for pretty much everybody

Maybe you're allergic peanuts. Maybe the mere sight of a FODMAP is enough to bloat you for days. Or maybe – just maybe – you've never tried a diet where you're actually allowed to indulge every once in a while.

If you fit any of those categories, then flexible dieting is likely to be right up your alley as it really helps to improve not only what you eat – but how you see food in general.

"I find that this nutritional approach works for just about anyone," says Louise. "It can even help to reduce bingeing tendencies for some and promote a healthier relationship with food through removing restrictions and 'good' and 'bad' food labels."

Although weighing the bulk of your food and punching it all into an app can have a downside for those who find themselves getting neurotic about every last morsel that passes their lips.

"The only people who I wouldn’t recommend it for are those who tend to become obsessive easily and would spend every second rearranging their food diary to hit each macro to the gram," says Louise.

"Flexible dieting is meant to be just as the name suggests… flexible!"