In a fast-paced world, demand for tasty, convenient food "to go" has spiralled. Fast-food outlets now feature on most high streets across the UK.
But before you stop to buy your next cup of Italian-inspired coffee or a burger in a box, you might want to check how many calories they contain.
Did you know, for example, that consuming these two items could wipe out more than half of your daily calorie allowance?
Add a muffin and a milkshake to the order and you could have your full quota, even if it's still only lunchtime.
The government wants us all to think more carefully about what we eat, to stem rising obesity rates.
It's asking fast food and other restaurant chains to put calorie and other nutrition information on menus.
McDonald's is on board and is this week installing calorie-content displays for every item of food and drink that it sells in all of its 1,200 restaurants. Starbucks has also signed up to the government's responsibility deal.
Dietitian Helen Bond says the figures might come as a surprise to some: "People don't necessarily realise what they are consuming.
"Without clear calorie labelling, it is easy to see how someone might consume - without any guilt - an entire day's calories in just one sitting.
"It's the calories that you do not factor into your daily diet that are most dangerous. Liquid calories are often the ones that creep in. They are easier to consume quickly."
The trick to keeping within the daily limits, she says, is knowing what choices to make.
The average adult male should consume no more than 2,500 calories a day, and women no more than 2,000 calories a day, according to guidelines.
So, if you go to Starbucks for a coffee and pick an Americano, which contains 17 calories, you will still have lots of your daily calorie allowance left for meals.
But pick a Starbucks' Signature Grande Hot Chocolate loaded with whipped cream and 556 calories and you'll wipe out up to a quarter of your allowance.
If you are feeling peckish at the same time and decide to buy a Fairtrade chocolate chunk shortbread to go with your hot chocolate, you'll hit half of your quota for the day as a woman. Even a skinny muffin will add 344 calories to the total.
Yet a fruit salad from Starbucks will only set you back 95 calories.
Similarly, go to McDonald's and buy a large cappuccino and a grilled chicken and bacon salad for your lunch and the calorie count will be 285. But opt for a Big Mac with large fries and a milkshake and you'll have consumed 1,450 calories.
Ms Bond says: "You can see how things can quickly top up. If someone was to eat 500 extra calories a day above the recommended amount every day for a week, they would put on about a pound of weight."
If this pattern continues for weeks or months on end, it is easy to see how someone starting at a healthy weight could become overweight or obese.
But it's not just the number calories that we should be concerned about, it's also how much salt, fat and sugar is in the food that is important.
"It's true that calories are calories regardless of where they come from, but you are more likely to pile on the weight if you eat energy dense food - stuff that's high in fat," she explains.
If you eat a gram of carbohydrate, this equates to four calories. But a gram of fat equals nine calories.
"So if you eat 100g (3.5oz) of chips, that would be about 190 calories, which is twice as much as 100g of boiled potatoes."
Ms Bond says it is possible to still enjoy fast food and stay healthy. One way is to make sure you keep track of what you have consumed and compensate if you need to by having a lean salad in the evening instead of a calorie-rich meal.
"Having calories displayed in restaurants and on food packaging will make a difference to those who want it to. It empowers people to make choices and take control of their own health. And it might make some people reconsider what they are eating."