Avoid the middle isles
With supermarkets, most people will shop through them by going down each isle. A large section of the store (mainly the middle third isles) will be full of unhealthy, processed, sugary and just poor foods and drink. As those isles have the most 'traffic', those are the most popular foods and drinks that are bought. They also advertise unhealthy foods throughout the supermarket far more than they do with healthy foods. Stick to the outside isles - that's where you'll find vegetables, fruit, fish and meats.
Have a list
Many will think of having a shopping list as being 'old school', but it's still a popular tool used when shopping. Not knowing what you want/need to buy will mean you'll end up buying things you don't need - often unhealthy products that are on offer. You don't have to walk around with a notepad and pen (which is kind of 'old school'), as nowadays you have shopping list apps that are more than just bullet points (they can be linked to multiple devices, shared with partners etc). Having a shopping list will help to keep you on track when it comes to buying your groceries.
Go shopping on a FULL stomach
If you go shopping when you're hungry, there’s a fair chance you’re going to be craving bad foods (not many people crave chicken breasts when they're hungry!). This means that you're far more likely to stick to the 'bad food isles', so make sure you have a good meal before going for your weekly shop.
Buy whole foods
Firstly, what are whole foods? well, they're foods that are nothing but themselves - carrots, peas, broccoli, eggs, chicken breasts, oranges, bananas, salmon fillets and so on. These are foods that aren't modified, they are what they are, and they're healthy (the vast majority of them). By buying whole foods, you're going to be eating far fresher and healthier foods, which is extremely beneficial to both your health and fitness goals.
Read the nutritional information
This tip is one that some people may think is a little tedious, but it's important. If you just throw any product into your basket without checking what's actually in it, then you're simply guessing what your putting in your body. It doesn't take long to have a quick look at the nutritional content of products. You want to mainly look at the overall calories, protein, carbs and fats. With the carbs, have a look at the figure underneath as well (usually says 'of which sugars' or something similar). This figure is important. Some products claim to be healthy and say 'low fat!', which is great if it is actually low fat, but if it's loaded with sugar then it’s not healthy. Reading the nutritional content is a very good and healthy habit to develop.