Loved by fitness fanatics, the thrifty and eco-warriors, there are now 8m posts of pre-prepared meals on Instagram, arrayed in rows of colourful Tupperware. But is it good for you?

The relationship between food and social media was once straightforward. Those were the innocent days when no meal could be declared consumed unless it had also been photographed, filtered and posted on Instagram, when the world seemed merely a stage for avocado toast, açai bowls and barista art. It was a different time – a time before meal prep.

While meal prep has long existed, of course, it has grown in popularity over the past six years, aided by Instagram, where there are 8m posts with the hashtag #mealprep. Most show a variety of meals prepared for the week ahead – quinoa salads, chicken rice bowls, carrot sticks, broccoli florets, hulled strawberries – all displayed in a selection of artfully photographed Tupperware-style containers.

Behind the glamour of such posts, meal prep is a simple concept: set aside a day of the week to prepare the bare bones of your meals for the following week, then store it in containers in your freezer or refrigerator until its allotted day. The theory is that it saves time in the busy midweek when the idea of cooking from scratch feels draining. It also saves money by encouraging home cooking and reduces food and packaging waste. It is favoured by those who wish to control portion size and calorie consumption and those following, say, a high-protein diet. In short, it is beloved by fitness fanatics, the financially thrifty, the environmentally minded, the nutritionally conscious and, of course, wellness bloggers.

Charlie King, 32, is a London-based personal trainer who appears regularly on MTV’s Beach Body SOS and ITVBe’s The Only Way Is Essex. By his own account, he has the kind of physique that is an advertisement for what he does. “I’ve got muscle mass, but I’m still athletic,” he says.

King came across meal prep six years ago, before he worked in fitness, while taking part in a shoot for Men’s Health magazine. “I was working with a trainer and meal prep has been a long-running thing with people who train,” he says. “He told me about prepping chicken, protein shakes, boiled eggs. It was so boring and bland, but it was the first time I did it and it was like: ‘Wow, it really is important to know these things if you want to be goal-specific.’ Diet is absolutely key when it comes to the whole shebang of keeping fit and meal prep makes it one more thing not to worry about.”

Facebook Twitter Pinterest Food for thought ... food prep is designed to save time in the busy midweek. Photograph: @floodeboor_fit/Instagram

These days, King goes “in and out” of meal prep. He has a base level of fitness and a breadth of nutritional knowledge that allows him to be a little more relaxed. But when he has a particular need to be at his physical peak he returns to a meal-prepping regime. “I’ve got a photoshoot in about three weeks’ time for my online coaching service, so in about a week, when I get back from Ibiza, I’ll be getting my containers out,” he says. “I’ll have two weeks of being very disciplined. I hate the word diet, but I batten down the hatches and focus on fueling my body the best way I can.”

For King, and most meal preppers, work begins at the weekend. “I always recommend to clients that Sunday is a great day to get organised for the week ahead,” he says. “It stimulates the brain. You can spend an afternoon on the sofa refreshing your phone or going down the pub, but what about going to the market, the fishmonger, the butcher, planning your week, working within a budget, thinking about packaging?”

He has a few tricks: “How you can make 30 mini omelettes in a mini-muffin tray, how you can cook eggs in bulk in an oven, how roughly two skewers would be enough protein for a meal, how blanching broccoli means it won’t go soggy after a couple of days,” he says. “You can be efficient and productive about it, but you can also make an afternoon out of it – work with your partner, put some music on.” The containers are essential. “There are many different sizes, with different compartments, which helps portion control,” King explains. “So you can weigh out X grams of meat or veg or salad.”

That demand for skewers, muffin trays and multicompartment containers has created a substantial market for Instagram-worthy accessories. British kitchenware company Lakeland says sales of its Colour-Match storage tubs have increased by more than 30% year on year. “You don’t want to be using old takeaway boxes,” laughs Megan J Elias, the director of the Gastronomy Program at Boston University and the author of Stir It Up: Home Economics in American Culture. “And you have to have the right mason jar for that farmhouse aesthetic.”

Showing off our food is nothing new – think of the Victoria sponges, raspberry jams and prize onions of a village fete, of buffet spreads and the relentless peacocking of dinner parties. “We always have a Martha Stewart impulse in a society – we want to make something and we want to show everyone we made it and it looks great,” Elias says. “People will do that for ever and always have. But Instagram adds another level.”

This is the strange puzzle of meal prep. On the one hand, it appears another symptom of an ostentatious, aesthetically preoccupied age, in which one cannot simply eat healthily, but must do so in a way that is meticulously curated and visually pleasing and then posted about on the internet. On the other, there is something so curiously old-fashioned here – a return to the culture of the weekly shop, the rhythm of meal planning and home cooking – that it is hard not to view it as a reaction to the age of instant gratification;, a rejection of the world in which every kind of cuisine is available to us at any hour of the day.

It is striking how many men have embraced the trend. “It’s part of a larger shift in masculinity and part of the de-industrialisation of society,” says Elias. “Manliness is uncoupled from manual labour. And, since the 80s, cooking has been a thing that both men and women can be impressed by. So, men are now cooking. But, of course, they take it over and it becomes competitive.” For those who can find neither time nor inclination to spend their Sundays slaving over a hot mini-muffin tray, there is the promise of a meal-prep delivery service, where all the chopping, dicing, measuring and boxing has been done for you.

Facebook Twitter Pinterest Food prep could serve as ‘a bridge for people who didn’t grow up cooking’, says Boston University’s Megan J Elias. Photograph: Alamy

The biggest of these is HelloFresh, which launched in the UK six and a half years ago and now has 1.9 million customers worldwide. Co-founder Patrick Drake says the company ascertained that it was “all the stuff before cooking” that put off people who felt they could not cook or did not like cooking. “It was the meal planning, the trudging to the supermarket, the buying ingredients in bulk that never get used up,” says Drake. What meal-prep delivery gave them, he argues, “was a feeling of achievement” untouched by ready meals or takeaway. “The slightly intangible thing is that little moment of victory when they stand back and say: ‘I made that!’ It’s a satisfying thing to take raw ingredients and turn them into a beautiful meal.”

For all its peculiarities and showiness, #mealprep might serve as “a bridge for people who didn’t grow up cooking”, says Elias. King agrees: “If you’ve fallen out of touch with how food is made, meal prep can help you find it again.”

Even those who have made a career exploring the sensuous pleasures of food are not necessarily horrified by the trend. “It’s sort of Lego cooking, isn’t it?” says the food writer and Great British Menu judge Matthew Fort. “But anything that encourages people to cook meals from scratch must be a good thing. It’s also a useful way, if that’s your bent of mind, to control how much you eat and your calorie intake – though I personally find that rather depressing.”

King encourages prospective meal preppers to ignore the pressures of social media hashtags. “Don’t be one of these Instagram-happy people with their overnight oats,” he laughs. “Not everyone has the time, money and energy to do it like that. I think food is something that should be enjoyed; it’s important not to get bogged down by it.”

But meal prep is not always as wholesome and benign as it may seem. For those who already have a disordered approach to eating, it may be a way to impose further control on food. “I think this kind of trend on social media does present a risk for people with eating disorders,” says Tom Quinn, the director of external affairs at eating disorder charity Beat. “It appears to be describing food in quite a controlled way. We know from people with eating disorders that this comes out of quite an obsessive approach to food – calorie counting or seeing foods in terms of ‘good’ or ‘bad’. So, yes, we are concerned. For people [who already have] an eating disorder, this way of describing food can be quite dangerous. We know that competitiveness and perfectionism are quite common among people with eating disorders.”

Some degree of meal prep can, however, play a role in regaining a heathy relationship with eating. “It’s common for those with eating disorders as part of their recovery to have input from a dietician or a trained professional and to have meal plans as part of quite a structured approach,” Quinn says. “For people with eating disorders, there can be some anxiety around spontaneous approaches to eating – for example, going to a restaurant where you don’t know the menu. So, some structured plan over a week, where you know this is what you are going to be eating and these are the ingredients, can be helpful. But this is only done with support and guidance with a trained professional. We would never recommend just going on to Instagram and seeing what someone else’s meal plan is.”

I traipse through the internet in search of meal prep ideas: pretty mason jars filled with layers of fruit and granola, black rice sushi rolls, sweet potato chunks held in airtight plastic containers in shades of sapphire and frosted crystal. It is a world that seems potentially bright and crisp and exciting.

At some point, I follow a link to a story about a woman in Australia who preps a month’s worth of family breakfasts and lunches in just four hours for approximately $60 (£34), but when I look at the pictures I feel crestfallen by their beigeness: puff pastry pinwheels, cheese sandwiches, containers of macaroni cheese. This, I suspect, is the more prosaic reality of meal prep.

I think of something Fort said when we discussed the trend’s potential drawbacks. “The only major criticism is that it removes the instinctive and creative part of cooking,” he says. “What seems a brilliant idea when you plan on a Sunday night might seem rather less desirable when you get to a damp, cold, wet Thursday. For me, part of the pleasure of cooking is the instinctive response to ingredients, of looking at something and thinking: ‘Ah! What shall I do with that?’ And so, for me, it might be a little sterile. Because the idea of eating for pleasure, for joy, for happiness, a sense of community, seems a pity to lose.”