This is what five-plus years of dedicated human guinea pigging has taught me.

From fasting to fake shakes, sugar-free to fermented, from HIIT to CrossFit, functional fitness to flexercise, we're flooded with new information and fads every day.

What works? What is right?

Very little, is the conclusion I've come to. At least in a prescriptive way.

This is challenging to get our heads around because people in fitness and food love to be prescriptive.

Yes, more greens less junk, more water less booze, move more sit less, prioritise sleep.

These rules aside, I've found that one approach does not work all the time for every one.

I've been vegetarian since I was 12 and never touched a supplement (unless it was for a story and I've never been convinced they made a difference). The next person goes vego and is almost instantly anemic or overweight.

Similarly, different bodies respond differently to the same diets or fitness regimes.

Something that works well for you at one point in time can be disastrous at another – for instance, if we're chronically stressed, hard exercise can hinder our health and weight as it strains an already strained system, spiking cortisol and slowing metabolism.

I used to be very focused on what I ate and how long I worked out. It was rigid and, for me, it was wrong.

I don't do gluten-free or sugar-free, although I've tried both. I like green juices but not juice 'cleanses' but I do think there's something to intermittent fasting. I don't count calories, I look at ingredients and I try new things but am rarely ruled by them.

I move every day but I don't always push myself to the limit. I pursue fresh air and pleasure in activity - it's about of a feeling not an appearance. This works for me, not for everyone

Others in the health and fitness world have done plenty of their own guinea-pigging, so I wondered what their biggest take-home health lessons have been.

Libby Babet of Agoga and bufgirl.com 

Babet has done plenty of experimentation with her diet and fitness as a result of health problems, injury and plain old curiosity.

"I've gone strictly paleo, tried living 100 per cent gluten and dairy free, given the FODMAP diet a go, tried herbal cleanses, gone high fat and low fat, managed macronutrients and calories, then ignored them completely," she says, adding she now takes a "wholefoods approach to eating and I'm not afraid of any food group" but avoids refined sugar and processed foods.

She has taken a similar approach to fitness, trying everything from bodybuilding to sprinting to dancing and believes it was important to understand how it affected her first-hand.

"At the end of the day, what I realise now as a more experienced trainer is that every single person and their genetics are unique and it's about experimentation, figuring out what's right for each individual," she says.

Genetic testing has been an eye-opener for the trainer.

"We have worked very closely with a few companies that have provided genetic testing for our clients and athletes. Seeing all the individual results come back has been AMAZING! Every single person is so different and what makes their body work optimally varies greatly.

"Different people metabolise fats, proteins, carbs, alcohol, caffeine and sugar so uniquely and you can also tell how prone a person is to injury and how much exercise they should be doing to optimise their workout routine – it is SO fascinating. It really proved to me that nobody is the same and blanket approaches do not work for everyone."

Guy Lawrence and Stuart Cooke of 180 Nutrition

Like Babet, Lawrence and Cooke say genetic testing has transformed their approach to their fitness and diet.

Through testing, Lawrence learned his individual carbohydrate tolerance, noting "everyone's is different" and discovered that he has "poor recovery which has changed the way I exercise and eat".

Specifically, the former CrossFit-nut gave up extreme exercise that was causing his body to deteriorate, for yoga.

The shift has given him a more holistic attitude to health.

"I'm much more health focussed now and not driven by ego or vanity," he says, and learned "the importance of downtime from technology, to de-stress and get outside and be in nature often."

Co-owner Stu says DNA tests along with simple food sensitivity tests, gut tests and blood tests have made a difference for him.

"Gravitating to the hottest high-street diet is not the way forward (individuality is the key)," he says, noting that he has changed his diet to manage various food sensitivities and now feels "amazing".

DNA testing revealed "that it is virtually impossible for me to gain weight (whippet gene) but that I am susceptible to future diabetes so I follow a low sugar approach to eating", he says, adding he has also cut back on endurance exercise.

"Now I lift weights for a very short period of time (30 mins max) and feel much better."

Ben Lucas of Flow Athletic

Former Cronulla Sharks' player and ultramarathon-addict Lucas originally turned to yoga for recovery.

It soon became an "integral" part of his training and combining yoga with high intensity interval training (HIIT) and TRX (resistance training using bands or ropes) provided a more complete workout.

Lucas believes one of the primary problems in people's approach to fitness is "high intensity training everyday or focusing on only one type of exercise without yoga or mobility work to help the body recover".

"Recognise you don't need to do long workouts to get great results," he adds. "We are big believers in HIIT in our strength classes – intense interval workouts for shorter periods."

Short workouts are a relatively new fashion, following fad diets are not.

"New fad diets enter the fold regularly and it's important to realise they're not sustainable and usually the weight returns when the diet ends," he says. "A balanced diet with fruit and vegetables is so important for long term health and wellbeing.

"When eating this way, you do not need supplements because you're getting all the nutrients you need."

Michael Cunico of Fitness First

Many of us learn the hard way about what our bodies do and don't like.

For Cunico, a former soccer player who is now the head trainer for Fitness First, it has been no different.

"Illness and injuries have taught me the happy balance between workout time, intensity and total weekly volume," he says. "Quality over quantity... is something that I aim for when exercising.

"Well known Sydney based strength and conditioning expert Tony Boutagy​ also has a phrase I like, 'you've got to burn it to earn it'.

"Being selective with the foods you eat (and the liquids you consume) might mean that missing your workout today does not adversely affect your fat loss or weight management goals."

For Cunico, this means "if I don't feel like training I don't".

"While at times we need to train when sore from a previous workout or fatigued from a long day, but if my body just doesn't feel right I won't train," he says.

"Or my workout will consist of simple movements, without load, low intensity movement and gradual 'stretching'. I tend feel these are useless during the workout but I never feel better than I do at the end of one of these 'work-ins' as opposed to a workout."

A work-in (or workout) also provides the chance for time-out, away from his phone (and selfies) and the busyness of life.

"It's a pleasure, your time, leave the phone in the locker and be alone with your mind and body, you will never look back."