Bridget Benelam, senior nutrition scientist at the British Nutrition Foundation, conceded that it can be hard to keep track of calories, with many foods - particularly takeaways - containing far more calories than many of us realise.
"It's a great idea, if you can, to try to cook more yourself," she advised. "You could perhaps try to cook a bit extra at the weekend and then freeze it so you've got some to use during the week. Then you know what's going in your food."
Ms Benelam suggests reading up on the types of food that contain large amounts of calories and limiting the number of oily sauces and creamy products in your diet plan, as these "can really pile on massive amounts of calories in a small portion".
Another trick is to base your meals around the kinds of food that fill you up and ward off hunger throughout the day.
Grocery items that are recommended include fruit, vegetables, low-fat dairy products, lean meats, pasta and potatoes, while ones to avoid include cakes, biscuits, crisps, sweets and even wine.
According to Ms Benelam, there is "really good evidence" that low energy density foods can help with weight control.
"The good thing about that is that you can eat really decent, satisfying portions that keep you full, compared to the very tiny amounts of high energy foods that are really unsatisfying," she explained.
However, it's not just your diet you need to think about if you're keen to achieve the perfect bikini body, as exercise also plays an important role.
"When you're thinking about your daily life and your leisure time, it's important to think about how you can get up and move around at least once an hour and not spend hours sitting," Ms Benelam observed.
She added that even small amounts of movement, such as walking for a short period of time, will over time contribute to a more active lifestyle.