Fruits are full of plenty of vitamins, minerals, fiber and antioxidants, which are nutrients that are good for your immune system, helping protect against disease. Of course they're a healthy addition to your diet, although they shouldn't be the only thing you eat. Consuming only fruit could disrupt your digestive tract, make it difficult for you to maintain your weight and possibly leave you malnourished.
Fruit makes a healthy addition to any diet, but alone can't meet all your nutritional needs. An all fruit-diet may lead to malnutrition, bowel discomfort and changes in weight.
Bowel Discomfort and Irregularity
Fruits are loaded with fiber. While you need fiber to keep your bowels moving, too much of a good thing causes problems. You could experience bloating and gas as your system tries to deal with the fiber overload. Belly cramping may soon follow.
Your intestinal tract might pull in extra fluid to help the big fiber dose pass through easily, leaving you with diarrhea. Or it could have the opposite effect. All that fiber could back things up, making you constipated and unable to pass stools for days.
Weight Loss or Gain
Eating only fruit could lead to weight loss initially, but could lead to your body going into starvation mode where it breaks down protein, and thus muscle tissue, for energy.
On the other hand, if you're not monitoring your portion sizes, you may be taking in more calories than you're burning off. This can happen if you're eating lots of high-calorie fruits like avocados, which have about 320 calories each; grapes, which provide roughly 230 calories in 2 cups; or papayas, which contain around 150 calories each.
Vitamin or Mineral Deficiencies
Fruits have high amounts of many vitamins and minerals, but they don't provide everything you need. With a fruit-only diet, you won't get vitamin D and may only get small amounts of bone-building phosphorus, magnesium and calcium.
Ultimately, this could lead to weak and fragile bones. You'll also be lacking in some of the B vitamins, particularly B-12, riboflavin, niacin and biotin. Without these vitamins, your body will have a hard time making red blood cells and converting foods into energy.
You probably won't be getting enough vitamin K either, possibly creating problems with blood clotting. Plus you may become overly fatigued because you most likely won't have enough iron in your system to deliver oxygen to cells.
Other Malnutrition Issues
With the exception of avocados, the majority of fruits have only a trace amount of fat. You actually need fat in your diet, particularly the heart-healthy mono- and polyunsaturated kinds. Fats help your body absorb and store the fat-soluble vitamins A, D, E and K; create hormones and enzymes; protect vital organs; and stabilize your body temperature.
When fat is lacking in your diet, you could become malnourished and start having complications with these functions. Your protein intake could also fall short in an all-fruit diet. Without adequate protein, cells and tissues can't function and could start to break down. You may also have problems with growth, wound healing, nerve signaling and digestion.
Read more: 5 Tricky Fruits and How to Eat Them