First thing to keep in mind is that there really is no "can" or "can't". I believe you can eat what you want, in moderation, as long as you compensate for it some other way in your diet and/or exercise.
Second, no one here can tell you how much you can eat of something. If you want someone to tell you what to eat and how much, you will need to consult with a dietician or follow a printed diet...but FitDay does not have that. Perhaps your doctor could give you something.
That being said, and my not being sure of what fruit loaf is (but Google tells me it is like what we refer to as fruitcake here in the states), I would say that it's not your best choice. I presume it is made mostly with white flour (simple carbs), dried fruit (very calorie dense), sugar (simple carbs), and probably alcohol (again, caloric). A better choice, if you are looking for one, would be a piece of whole-wheat bread with some peanut butter or almond butter. That would give you a complex carb, a protein, and some fiber to boot. It would not hit your blood sugar like a ton of bricks like fruit loaf would, would keep you fuller longer, and would be much more nutritious. A piece of cheese and an apple would be good as well, or some almonds and some fruit.
If you have to ask yourself if something is a good idea to eat, go look at your profile where it tells you how many calories you should be consuming in a day based on your current weight and goal weight. Then look at the food in the food list. If your calorie limit is 1400, and what you want to eat is listed at 500 calories, then you've just blown over a third of your calories on that...but only you can decide whether it's worth it or not.
The basic rules I try to follow are to balance carbs, protein and fat; make the carbs complex (whole grain, fruit, vegetables), make the fats mostly unsaturated, make the proteins lean (i.e., chicken or fish as opposed to fatty ground beef or steak) and make sure I get at least 25 g fiber a day. But everyone is different.
It is a universal truth, though, that simple carbs and too much fat will pile the weight on you and provide you with little nutrition. If you look at the nutrition information on the foods you want to eat, all the info you need to make your decision should be right there.
One website I really like is Food facts, nutritional information, nutrition, healthy eating, diet, food allergies, ingredients - Home
. This site gives everything a score from A to F. For example, Betty Crocker Brownie Mix gets an F and broccoli gets an A. It takes a lot of time and effort at first, but once you get to know your food (become a label-reader...seriously!!), the easier it will be.