Published in Spectator Health.

Summer is finally here and some of you may be thinking: now is the time to get properly fit. You already enjoy going for a run in the park — but you know you could do better. Time to build up that stamina, tone the muscles you don’t use when you run and generally instal a biological upgrade.

Time for a personal trainer! What could possibly go wrong?

Quite a lot, unfortunately. If you’re unlucky you could find that by the end of summer you can’t run any faster — because you can’t run at all. You’ve hurt your knee or your back is giving you real trouble — and your GP is saying: lay off the exercise or you’ll make it worse.

What’s gone wrong? Simple. You’ve picked the wrong personal trainer, which is a frighteningly easy thing to do these days.

Full disclosure: I’m a personal trainer. You may suspect that I’m just worried about the competition, dismissing my rivals as cowboys. But I’ve got no quarrel with trainers who know what they’re doing. It’s the guys who set up in business after weekend training courses lasting just six weeks who are doing the damage — real physical damage to the bodies of their clients.

I see it happening more and more often, in gyms and in the open air. Sometimes it falls to me to repair the damage: some of my clients have been badly injured by ‘trainers’ who pushed them into exercises that were completely wrong for their bodies.

I’ve coached since 2003; before that I competed as a parallel bars gymnast. I’ve trained men and women covering the entire spectrum of physical fitness, from terminally ill cancer patients to Bear Grylls. My parents are both doctors and I’ve spent a lot of time studying the relationship between lifestyle, nutrition and key medical indicators such as blood pressure and heart rate.

The UK fitness industry is largely unregulated, so here’s one simple piece of advice for anyone starting out with a trainer.

Ditch your trainer right away if you experience muscular pain during a workout and he or she tells you to ‘work through the pain’ by repeating the exercise.

‘No pain, no gain – let’s do another 50 kicks.’ I can’t tell you how many times I’ve overheard ‘trainers’ with minimal qualifications encourage their clients to do this.

These guys don’t know the meaning of repetitive strain. They’re adding to inflammation and muscular strain that – even without bad advice — is rising inexorably as our employers chain us to our desks and then we voluntarily put our bodies through the same contortions as we sacrifice our evenings to the computer.

To be fair, many people try to make up for it by taking unstructured exercise as recreation. It’s not the quickest path to overall fitness, but it’s far, far better than nothing.

If this exercise is a real pleasure for you, be warned that a rogue trainer may take it away from you.

There are plenty of clues to help you spot a poor trainer. Trainers need to know about (for example) blood pressure and cortisol levels; if they don’t, they could be preparing the ground for a medical crisis. But the ‘no pain, no gain’ nonsense is perhaps the most useful of all. As soon as you hear it, start running. Out of the gym.

All of us have fat that we can’t see. That’s because it’s hidden within our bodies. To see it properly, you’d need a body scan — a hideously expensive MRI scan or the more affordable DEXA (which stands for ‘dual energy X-ray absorptiometry’).

This hidden fat matters. For some people it matters very much indeed, because of what it does to their long-term health.

I explain this to some of the people I train. It tends to worry them, because they think their ‘slightly forward waist’ (as they put it) is cancelled out by their well-defined pecs.

Sorry, but no. Inside that slightly forward waist lurks a potential killer.

We’re talking about visceral fat, which is defined by Diabetes.co.uk as ‘body fat that is stored within the abdominal cavity and is therefore stored around a number of important internal organs such as the liver, pancreas and intestines’.

Another name for it is ‘active fat’, so called because it affects our hormones. It raises the risk for type-2 diabetes, which is why diabetes charities are so worried about it. Heart disease, too. Breast cancer. Colorectal cancer. Even Alzheimer’s.

So it’s nasty stuff, this visceral fat. Firm rather than squishy when you press it. It’s hidden, possibly suffocating your internal organs, but not truly invisible — because the best way to tell if you have too much of it is to check your waistline. Subcutaneous belly fat, easily spotted, is usually accompanied by something even more unpleasant within.

There are plenty of websites out there that will tell you how to check for visceral fat without going to the trouble of a scan. A tape measure is a good place to start.

But, as a personal trainer, it’s my job to take things to the next level: getting rid of the firm (not squishy!) killer in your abdomen.

If you think that doing lots and lots of sit-ups will get rid of your visceral fat, you’re deluding yourself. Like most forms of ‘spot reduction’ (ie, exercises where you concentrate on one part of the body), this is a waste of time.

Sit-ups, yes. As many as you like. But also exercises that involve bigger muscle groups and more than one joint movement — compound exercises, as they’re known. (If it helps, remember the phrase ‘compound before isolation’.)

So: squats, lunges, press-ups, pull-ups, dead lifts… and that’s in addition to aerobic exercises.

But we keep coming back to diet. Losing fat needs a steady calorie deficit, day after day. Exercise can play a large part in this, as I’ve said: I’m keen on ‘interval training’, in which you break up your steady jog with short, fast bursts. And do it consistently — three to five days a week.

However, your chances of achieving this deficit, and therefore of reducing visceral fat along with its squishy counterpart, are hugely increased if you eat a diet rich in plant-based foods, healthy fats and protein. All that hype about the Mediterranean diet? On the whole, I think it’s justified.

The exercise and diet recipe is really quite simple, then. But is it easy to achieve? That depends. It comes down to consistency.

I’ve trained clients who thought that one hard workout a week — with me, or at a weekly bootcamp — would do the job. It won’t. What changes visceral fat is regular training, sensible eating and patience, week after week.

The piece is about training for the mirror: big arms and chest, little attention to the legs and hips that actually carry you. It argues for lower-body strength, squats, lunges and hinges, as the foundation.

Whole-body cryotherapy was being sold as a quick route to fat loss. The column’s point is simple: a few minutes in a cold chamber doesn’t replace eating well, training consistently and sleeping properly.