On the other hand, leptin (only discovered in 1994), is an appetite suppressing hormone which regulates our food intake and energy expenditure. If we didn’t have it, we would rampage around Waitrose, devouring Green & Black’s straight off the shelves.

A healthily functioning appetite depends on these two hormones balancing each other, but there are various other factors which have an influence on how hungry you’re feeling, too. If you are ill or jetlagged, certain protein molecules interfere with this process, and you should find it much easier to say no to a second helping of goat’s cheese lasagne. If you are at the most fertile point of your menstrual cycle, you’ll also feel full sooner, which scientists think this is an evolutionary trait – your body doesn’t want you distracted by foraging when you ought to be focused on getting pregnant.

Weather can also affect our appetite. We want to consume more calories when it’s cold, while sweet foods taste sweeter, spicy foods spicier and coffee more bitter in warmer weather.

But many of the responses we have to food are conditioned, rather than biological. If your mouth waters in anticipation of something delicious, it’s not because your body needs more calories. What we feel like eating comes down to culturally determined taboos and fetishes – coffee to feel grown-up, dairy to feel comforted, sugar for a brain addicted to the dopamine hit. Even the illusion of hunger or satiety can be psychosomatic. If you eat something you’ve enjoyed before, or if you are fooled into thinking your portion size was bigger than it was, it’s still likely to stave off hunger for longer.

If you’ve ever felt too hungry to cope with a supermarket, or charged round a convenience store only to leave empty-handed, this actually has a physiological basis. As hunger deepens, people become extremely irritable, aggressive and impulsive, and this can crystallize into a potentially dangerous stubbornness.

The Buffet Effect

But are we really feeling hungrier now than we used to? Yes and no. The average person in a developed country now has 500 more calories (2,750) available to them per day than they did 40 years ago – comfortably over women’s recommended daily intake of 2,000 – but because Britons live in better insulated homes, and do less exercise, we actually consume fewer calories than we used to. Despite this, we’re 22lbs heavier than we were in the mid Seventies. Regardless, there’s no denying that we’re more fixated on food and our appetite than we used to be.

Food has permeated our entire culture. Terrestrial TV dedicates 16 hours a week to cookery shows. There are two channels devoting their entire output to the larder and The Great British Bake Off averaged 4.56 million viewers a week last year. It’s not just TV – our bookshelves groan under the weight of our cravings. The fastest and bestselling non-fiction book in UK history is Jamie Oliver’s 30-Minute Meals. The Bookseller estimates that the food and drink category is worth a staggering £90.8 million, up from £55.5m in 2001 – and we’re not necessarily even cooking from them, leading The New York Times food writer and author Molly O’Neill to dub them ‘food porn’.

And it’s not simply the amount that food factors in our lives, it’s also its immediacy. We don’t have to wait for fruit and vegetables to come into season anymore, we can get anything, from anywhere in the world. Call it the buffet effect – if you have more food to choose from, you eat more (women are especially susceptible to this).

Why are we so hungry?