This is a really common question that I get asked as a PT. The answer?... we're simply talking about calorie deficits; burning more calories than you consume for a continual period of time, until we become a healthy weight. This should be done safely through a mixture of exercising regularly and eating a healthy diet, and whilst we all imagine a quick fix to be the best option, I can assure you that losing a steady amount of weight for a slightly longer period of time is better than shedding lots of weight really quickly!
Now, to be clear, I'm not suggesting that you stop eating completely, or spend several hours in the gym each day. It's not a healthy mindset to have, nor is it very realistic. Essentially, your body needs a set amount of calories (or energy from foods) each da in order to just function normally - keep the blood pumping, the brain working and the muscles moving. Therefore to do all of this, it is important to eat a minimum amount of calories per day. UK government guidelines suggest 2000 calories per day for women, and 2500 calories per day for men, on average. Remember that these are guidelines, so there may be a margin each side for alternative values. Government guidelines also suggest that everyone should complete 150 minutes of moderate exercise per week too (generally 30 minutes exercise, 5 times per week).
So, here comes the maths; many people can end up overweight because they are eating the calories that are suggested but lacking in the exercise department. Be honest with yourself; how many times do you get out of breath and perhaps slightly sweaty in a week for 30 minutes or more? If your answer is yes, but you're still eating the suggested calories (or more?!) each day, then it's unlikely that you're in a calorie deficit. Government guidelines then continue to look at those people that are looking to lose weight (safely and effectively I hasten to add); 1400 calories per day for women is suggested and 1900 calories for men. This can be met by exercising more regularly and more intensely, and by eating a healthier diet.
When it comes to tracking our food, apps such as "myFitnessPal" can be really useful (this isn't an ad, its just a really useful bit of kit!). It's been updated with hundreds of different types of foods, and knows all t