Eat well while you’re young, and you’ll set up healthy habits for life – a good idea in theory, certainly, though trickier in the offing. While the mainstays of a good diet apply no matter your age – everything in moderation, eating whole foods wherever possible and choosing from a wide range of ingredients – certain decades of life and the changes they bring, be they hormonal or lifestyle-based, can require us to sharpen our focus on particular areas. Here’s what to look out for at every age and stage.

Teens and twenties

Your metabolism slows with age – a decline that begins, according to Michael Jensen, who researches the subject at the Mayo Clinic, at 18. While there may be no better time for us to be laying the groundwork for good eating patterns, adolescents today are ‘a generation we’re a bit worried about’, according to dietitian Helen Bond, pointing to the low-iron diets teenagers, who often choose ultra-processed foods, are consuming. The requisite amounts – 11.3mg per day for boys and 14.8mg for girls – from foods such as red meat, leafy greens and wholegrains boost growth and muscle development while warding off ‘poor lethargy and concentration’.

‘Good foundations really are key,’ Bond says. ‘The more calcium that’s deposited in the bones during childhood and adolescence, the stronger bones will be in later life.’

The best means of defence is, says Dr Giles Yeo, principal research associate at the University of Cambridge and author of Gene Eating, ‘keeping in mind the rules of moderation’ and ensuring a diet rich in ‘fibre, which keeps our microbiome and bowel happy, and more unsaturated fats (ie avocados and oily fish) rather than saturated ones (such as processed meat and butter) – those are two golden rules.’ Keep an eye on sugar and fat consumption, he adds, but ‘don’t demonise any foods’ as this will only create deficiencies further down the line or bad habits for when short-term diets – the majority of which fail – veer off-course.

Thirties

Eating for two may sound exciting, but it is just one of many medical myths surrounding pregnancy, says Hollywood fitness instructor Simone De La Rue. ‘You will have cravings and that’s natural’ – she admits that pizza and ice cream featured among hers – ‘but like anything, you have to have discipline,’ she explains. Experts also warn of dangers of doubling your food intake, encouraging expectant mothers to maintain healthy levels of fruit, fat and fibre, while avoiding mould-ripened soft cheeses (such as Brie or Camembert), too much oily fish (no more than two portions per week), and partially cooked meat or eggs.

[Don’t pity me: She dines out alone for pleasure]

Stress is one of the biggest causes of weight gain and, as workplace pressures and the need to balance the personal and professional rise during this time of life, recognising the signs it may be derailing your diet are key. Being consumed with work can cause either disaffection with eating right or a hankering for options that are low in nutrients but high in saturated fats ‘in an attempt to fulfil emotional needs,’ according to the Mayo Clinic, ‘even when you’re not hungry.’ They advise asking yourself why you’re eating before that first bite: is it because your stomach really is rumbling, or to feel the warm embrace of slab of chocolate? Stress also directly affects the speed of women’s metabolism, according to 2015 research, with study participants who admitted to feeling under pressure in the 24 hours prior burning fewer calories than their peers, as well as resulting in higher levels of insulin, which contributes to fat storage – usually around the abdomen, which is linked to greater health risks than weight elsewhere in the body.

Forties

Middle age sees a ‘toxic mixture of sitting down all the time and having a lot of money to spend on food,’ Dr Yeo says, ‘and if you are at risk of type 2 diabetes or cardiovascular disease, you need to watch what you eat.

‘There’s a huge chunk of the population for whom diet-related illness is driven by lifestyle, and they make themselves most apparent’ at a time when ‘the bounciness of youth’ has departed, and four decades of damage set in.

Dr Yeo’s preferred method for ‘keeping the tide back’ is to ensure good levels of physical activity (if you haven’t already) which will not only keep middle aged spread in check, but combat diminishing muscle mass.

Sam Gregory, co-founder of F45 Stratford fitness studio, suggests ‘two good resistance training sessions and two cardio’ weekly, complemented by ‘plenty of healthy fats – nuts, seeds and good quality oils including olive, coconut and avocado.’ Gregory, 41, also takes a fish oil supplement, which ‘tends to help with cardiovascular health’, while opting for protein-based breakfasts instead of more carbohydrate-heavy toasts and cereals.

Fifties

On average, a woman begins menopause at 51, at which point oestrogen production drops, raising heart disease risk to the same level as men’s, as well as increasing susceptibility to osteoporosis. Weight, blood pressure and cholesterol must be monitored during this decade, which means cutting back on alcohol and caffeine, and picking low-sodium options where available for foods like stock cubes, baked beans and soy sauce at the supermarket.

With ever more research drawing links between our lifestyles and serious diseases from cancer to inflammation and hypertension, renewed focus on eating well and moving as much as possible must override the natural inclination to take your foot off the pedal. Processed meats like those found in a BLT serve, sadly, very little nutritional purpose.

Sixties and seventies

Retirement can provide a good point at which to recalibrate healthy regimes. Continuing a diet rich in calcium and protein sources remains crucial, due to the ongoing diminishment of bones and muscle: Bond advises plenty of kale, spinach, broccoli, eggs and brightly coloured fruits and vegetables. The latter, including oranges and carrots, are rich in carotenoids lutein and zeaxanthin, which are believed to boost eye health and protect against conditions like age-related macular degeneration, which can impair vision.

With life expectancy going up, ensuring that the growing number of years we have are good quality matters all the more. At every stage, ‘you need to find a diet and exercise regime – it’s not one versus the other – that matches your age in life’, Dr Yeo advises. Maintenance may not feel as immediately gratifying as shedding kilos thanks to a rapid diet, but the long-term gains of sustained good living mean you will see the proof in the (occasional) pudding.

In short...

Teens and twenties: Kale and fish, such as sardines, are a great source of calcium while red meat, helps to increase iron intake.

Thirties: Maintain a healthy diet including fruits and vegetables and avoid mould-ripened cheeses.

Forties: Complement weekly cardio with healthy fats from nuts and seeds and quality oil. Avoid carb-heavy cereals.

Fifties: Cut back on caffeine and opt for low sodium varieties of foods like baked beans and soy sauce.

Sixties and seventies: Eat a calcium and protein-rich diet of fruit and leafy greens, such as spinach.

Daily Telegraph