Depends what you mean by "eating healthy".
In my opinion, there are two types:
- first, the type of eating where you give up certain types of food that are universally known for being unhealthy and doing damage to the body
- second, the healthy eating which is based on your own body and metabolism and created by a nutritionist that got you through some tests first.
Our bodies are different and people should never forget that.
If your main focus is just to avoid "bad food" and start to exercise regularly or just to have a more active life, the effects should be as followed (if the eating is done correctly):
- if you are obese you will lose weight, if you are underweight you should gain weight, BOTH until you reach your ideal (known as average) weight; usually people think they need to be SKINNY in order for them to be HEALTHY; that usually does not go hand in hand;
- you will feel a lot better general state wise and about yourself;
- from my experience, you will also feel less tired, more energic and your mental capacities will improve in a more or less obvious level;
- you shouldn't experience any pain or negative state from either the outside or the inside of your body (such as pain in muscle, bones, headaches); if you are then something is wrong;
- you shouldn't be having any aftermath, like eating disorders or binge eating or mad cravings (that's usually the body signaling you that something is wrong once again); you should make sure that you have a balanced metabolism and that you ALWAYS listen to what your body says, both when it demands food, when something hurts AND when it feels good.