1.) Train Legs: Abs need good roots (pun intended), so training legs regularly will encourage your body to release greater amounts of growth hormone and testosterone, consequently your muscles grow more efficiently. More muscle mass increases energy demand thus increasing fat burning.
2.) Stay on top of the carbs: Carbs are not your enemy, however most people (particularly men) store a carb surplus on their mid section and lower back. So if you are looking to maintain or even uncover those abs, then be sure to moderate your carb intake. A good ratio is 40% carbs, 30% fat and 30% Protein.
3.) Limit weighted ab exercises: Although the abs are a muscle like any other, additional weight can actually hinder the process of uncovering your abs rather than helping! The abs will show themselves if the percent body fat is low enough, so the key is repetition and volume. Adding weight will increase thickness to the abs and will not necessarily reveal them, so aim to keep it to bodyweight if you want them to show year round!
4.) Diet: Diet is at least 80% of the battle when trying to maintain your abs. I have already alluded to the carbs, but the diet in its entirety plays a massive part in maintaining abs year round. A good rule of thumb is to consume 5-6 small meals a day, this controls the calorie and glycaemic load of each meal. A large intake of calories can cause exaggerated hormonal shifts which encourage the storage of calories as fat, as well as encouraging osmotic shifts of water to the mid section covering your hard earned abs! A good estimation for a calorie controlled, nutritionally balanced meal is to have a hand sized piece of chicken (for example), a fist sized portion of sweet potato and approx half of the plate as mixed veg.
5.) Vary the training stimulus: Variety is key here, it keeps things interesting as well as ensuring you hit all parts of the abs. Hanging leg raises, Cable twists, Oblique crunches, Rope upper ab pull down, Reverse leg raises and Medicine ball wood chops are exercises that will hit the rectus abdominus, Transverse abs and obliques. By performing these exercises and maintaining a calorie controlled, nutritionally balanced diet there is no reason why you can’t get yourself some evergreen abs that last all year round.