You know that situation when you’re out dining with friends and one orders the grilled fish. She always does.

And she insists on a side salad which no-one else wants to pay for. Another always has a big bowl of pasta with a big serve of warm bread on the side. Maybe even two. Another is waiting to see what everyone else orders before taking the plunge, making sure it’s the best, and there’s the one who has the deep fried fantasy followed by Tiramisu, all washed down with five wines and an explanation that is part boast, part guilt: "I just have a good metabolism."

And it looks as though she does. In many years of friendship she has barely gained a pound, wears beautiful clothes and eats up a storm.

But what’s really going on behind that treacherous diet may well be another story.

I went to school with a lot of people who ate rubbish but were thin. I wasn’t thin but had to look after myself so set about learning as much as I could about food. Now I look 10 years younger and they’re all overweight.

Eventually the bad food catches up with you. Again, this proves my mantra that it’s not always about the weight. Being thin doesn’t necessarily mean being healthy. I had an aunty who was always thin but she smoked like a chimney, drank too much alcohol and died at the very young age of 55.

The truth really lies in blood tests. That’s how we can get the best picture of what’s really going on with your internal organs, insulin levels and metabolic function. You really don’t have to be overweight to be unhealthy.

A bad diet will inevitably mess with your metabolic function, cause higher oxidation to your skin and will affect your gut microbiome – at some point. Even if you get away with it for a long time by not gaining body fat, I’m sure a blood test result would be either worrying or down right threatening.

There’s no great pride to be had in eating the unhealthiest options on the menu. The more we know about food, the more we look to food choices for insight about people’s mentality.

Is that just a plate of chips or is it a political statement? Maybe it’s a reflection of your emotional state, or an escape or 'I can eat what I want and no-one can stop me’ type of mentality. My favourite is 'I deserve a treat' or 'You have to live your life' or 'Life is too short.' I can tell you life will be very short if you keep eating junk food, processed food and a lot of alcohol and soda.

I have a different approach. I don’t think you’re living by beating yourself up with bad food. I don’t think it’s living to be basking in the glow of a beautiful sunset that you have to wash down with a bottle of wine. Really? Isn’t it good enough without the nasty trimmings? I also don’t think that living life to the full means ensuring you eat food that makes you feel fatigued, sluggish, depressed and irritable.

That’s not living 'all out'. It’s usually peer pressure. There are a lot of food bullies out there who like to call attention to the person at the table who’s eating the healthy grilled fish and salad, causing self-consciousness and that awful feeling of being in the spotlight and having to explain that, well, you just like it. The food bully is invariably the one who knows he or she isn’t eating mindfully so they want everyone to join the catastrophe to make it truly complete. Then, they feel validated about filling up on refined foods with nothing green or leafy in sight.

I often encounter people who want a break from healthy eating because they tell themselves they need a treat once in a while which prompts me to ask what is a treat really? Is it a treat to eat an inflammatory bunch of sugar that will have a negative impact on your body? Maybe you don’t believe it will do that much harm but, I can tell you, the science definitely says otherwise. There’s a reason people complain of a sugar hangover – because it’s real. It’s not just the main cause of obesity in the western world but, as a study from the 2014 JAPA Internal Medicine journal found, there’s also a strong correlation between a high sugar diet and dying from heart disease. The liver metabolises sugar in a way that converts it to fat, often leading to fatty liver disease and being a major risk factor of diabetes as well as heart disease.

So, for me, a treat is one of the countless ways to do something for myself that’s actually good for me, not destructive. Or if someone wants to offer me the treat, that’s fine too. I’m not fussy where it originates but it’s not going to come from the cake shop or pizza restaurant. It’s carving out time to do something really nice for yourself. A treat is to be kind to me. It’s making time to exercise in whichever way I chose in a beautiful park or in the country, getting my nails done, a soothing pedicure, feeling really good in my skin, buying beautiful food at the market, getting a massage. It really isn’t shoving sugar or alcohol in my face. That’s not a treat. It’s a cry for help.

We’re so conditioned to think a treat or a cheat meal is understandable, permissible or, my favourite, deserved. It’s really just a way to set yourself up for failure. So, ask yourself what does a treat really mean to you? And, maybe you’ve never gained weight from the fake, rubbish, food but the whole picture may not be visible to the eye or on the scales. It will be having a negative effect somewhere at some time. It’s just a matter of when.