Everything needs a measure. In the same way as before any diet, before you take in large quantities of anything (and even healthy fruits!), It is better to go to a therapist, get a series of tests and make sure that it suits you. For example, fresh juices are believed to be useful. However, they can do more harm to certain people, because natural acid can provoke an exacerbation of gastritis or ulcers. Therefore, it is better to play it safe and, in order to improve health, do not lean on fruits, but use vitamin complexes.
My philistine opinion, only as a former graduate of the medical institute. - Depends on how well you are eating now.
If you eat a lot of high-calorie fatty and sugary foods, then there is every chance. Simply due to the fact that the volume of eating that very high-calorie one may decrease ...
And so - well, fiber, the intestines will work cheerfully. So if there are no problems with this now, then this "plus" does not matter.
Vitamins? There is, of course, some amount of them in fruits, but unpredictable (how much was stored, how it was grown); and one tablet of multivitamins a day solves the problem completely and guaranteed.
In a word, there will be real benefit only in the first case: if you are eating poorly now (EXCESSIVE high-calorie / fatty / sweet), and if the fruit is moved to the diet "the wrong" food, not just added to it.
It depends on what kind of fruit. It depends on how much more. It depends on how much the diet as a whole has changed. Maybe there are contraindications to a lot of fruits?
Nutrition is a very complex topic, therefore it is impossible to simply say so unambiguously. For me, for example, it was a great discovery that for some very common diseases, spinach, which is considered almost a panacea, or grain bread, as it is considered, is healthier, is not allowed.
The main answer to the question is: yes, health will improve. But! now there are few conditions for a correct and beneficial effect. The most important thing: do not overeat, it is not known how much fruit you eat now, maybe already a normal amount. There are many options for info graphics on the benefits of fruits. Find several such schemes and use them. Surely the sources should be scientific research, not dietitians and all sorts of trainers and traditional healers, only science, which knows how this or that fruit, its composition, affects a person. Decide on the fruits you want to eat and find all the information on them, and then eat to your health!