First, see a dietician that specializes in obesity. This can not be stressed enough. If you're in an exercise program make certain that the frequency and type of exercise are accounted for.
Most research for the past 15 years seems to indicate that you will get the best loses at 75-80% of your estimated burn rate. Base Metabolic Rate (BMR) + Calories from exercise. There are some minimums regarding bodily functions that you should stay above, around 1200kcal for women and 1800kcal for men. Well over 100g carbs/day (unless going ketogenic, don't do this if you're diabetic) and 0.8 - 1.2 times your lean weight (in pounds) in grams of protein per day, more if exercising heavily. Fats need a mix of different fatty acid chains (omega3/6, etc) and should be above 50g a day, minimum. Minimal sugars, avoid all refined sugars. (Again, talk to your nutritionist).
If you do less than the above minimums, your body's metabolism will shift, and will have to work harder to create the nutrient chains that it needs. Either from other sources when possible, or by cannibalizing fat and muscle stores, etc. Some nutritional needs are difficult or impossible to synthesize and will present as various malnutrition symptoms.
Some plans will have you go VERY low calorie (under 600/day) this forces your body to use it's own resources in order to lose weight. You will lose lean muscle in addition to fat if you do this, and should not do it for more than 2-3 months at a time. You will also be at risk for various malnutrition diseases. This is a tactic used when extremely obese with the theory that the fast lost and associated risks are outweighed by the long term benefits. If you are advised to go this route, make certain your various vitamin, electrolyte and other indicators are tested before and throughout this process, you will need to take supplements, and your absorption will vary.
From what I've read, it's far better to have an appropriate calorie load, with some attention to your macro needs, and a variety of food. With modest additional exercise and an appropriate caloric intake you will have the best results over time. You should reevaluate your burn rate (BMR + Exercise) every 1-3 months as you lose weight, or if you plateau for more than a few weeks. It will be lower for your resting burn rate but you should be able to be more active.
Get enough rest and push yourself now and then. Make sure to have a rest day or two a week you can do some cardio, but not a full load workout.
Now for the macros, your dietician can guide you... If you join a cross fit (boot camp) program, or other heavy program with a lot of weight and resistance, you definitely need more protein than carbs... Your dietician can guide you to a good range to strive for.
I'm around 400# (us) and 6'1" tall. My resting burn rate is 3300kcal and I'm burning another 800-1100 on training days. My own targets are around 3000-3400 intake on training days and around 2000-2500 on down days. My macro ranges are 150-200g of carbs a day, avoiding sugary fruits and refined sugar. I get 250-300g protein per day and 100-160g fats a day.
Now you weigh less than half what I do with a much closer target, so your calorie needs are probably closer to half, which is the suggested level for women near a healthy weight.
My own dailies are as follows...
Wake up and have a serving of bcaas, with a protein shake, 2 scoops whey and a banana, 2tbsp pbfit, and unsweetened coconut milk and a tbsp of coconut oil and 2tbsp flax meal.
Morning snack is about 1.5 servings of medium digesting protein, I have chicken most days, but if you eat egg whites, that works (will do 3 whites, and one whole egg hard boiled).
Lunch is usually a salad with extra protein, I and a carb side in training days. Quinoa, lentils, beans, etc preferred over bread/rice.
Afternoon snack is another protein shake (double size) no banana with water. Then a pre workout supplement with bcaas.
Gym training is about 40-55 minutes...
Post workout bcaas, creatine as one scoop protein. Along with a banana, 1-2oz mixed nuts (no peanuts) and a cup of kefir.
Last meal is a large salad with cottage cheese.
Your portions and needs will be very different... The final meal is dairy protein which trends to be about 20%whey and 80/ casien. This is for slow digestion and continued muscle rebuild over night... The carb (banana in the morning with fast acting whey and a fast acting carb is a good fasting recovery) a medium protein for morning snack to stay anabolic, and a healthy lunch, complex carbs are best here for the energy working out later. More fast protein to stay anabolic and prep for workout... The workout is rough... Post workout is a mix of protein and mostly fast carbs... This helps replenish glycogen stores with enough protein to keep your body working.
I've been at this for 3 weeks now, down about 24# and about 1# muscle added, ymmv. I'm starting from a very different point. You didn't mention your gender or age. I stalled the second week which is when I was told to eat more... Again, 75-80% of calories burned. With a variety of different fats, proteins and carbs.