Eat less, move more, it really is that simple.
The only way to lose weight is to be in a calorie deficit, by taking in less calories than you burn.
“This study showed that independently of the method for weight loss, the negative energy balance alone is responsible for weight reduction.” (B Strasser et al. 2007)
That being said you won’t out train a bad diet. Most people are unaware of the calorie density in many processed foods and how much exercise you would have to do to burn it off.
example, a KFC box meal has 1,030 calories, whilst the average man will only
burn around 590 calories running 5 miles in an hour. You’d have to run almost
10 miles at this pace to burn off that one meal! Nearly 2 hours of non-stop
running at this pace.
The foundation of weight loss is nutrition. However, this doesn’t mean you should skip on exercise. Both cardiovascular and resistance exercise have their own health benefits as well as adding to that necessary calorie deficit. Resistance training can over time, also increase muscle mass and therefore increase your basal metabolic rate, meaning you need more calories to stay the same weight & can therefore eat more calories without adding excessive bodyfat.
If you are struggling with your weight you should consider hiring both a nutritionist and a fitness professional to help you achieve this goal.
B Strasser, A Spreitzer,P Haber. (2007). Fat loss depends on energy deficit only, independently of the method for weight loss. Annals of Nutrition & Metabolism. 51 (5), 428-32.