The best way to change your bad nutrition habits is to do it very slowly. If you try to change everything all at once, it will seem too overwhelming and hard to maintain. Try changing one thing at a time.
For example, perhaps you like a morning cappuccino on the way to work. Make a small change by deciding to stop drinking your morning cappuccino and drink bottled water instead. Don’t change anything else about your nutrition habits until you feel totally comfortable about that dietary change.
Then move on to something else, like healthy snacks. Instead of that chocolate energy bar, pack a piece of fruit and a small tub of yogurt. Essentially fruit is natures snack food, it’s also cheaper.
Once you’re comfortable with this healthy change, and then move onto something else. You get the picture. When you’ve got your diet sorted out and are consuming more healthy food to aid in your nutrition, and then be sure to get some exercise into your lifestyle.
So it doesn’t seem to be such an abrupt change, you just need to understand more about what your food and what the energy value is and the nutrient value of what you are consuming, and make slow but lifelong changes to your lifestyle.