What is your height? 100 kg is excess at any height. You should aim to lose your weight slowly and steadily. Firstly rule out conditions like hypothyroidism which can lead to excessive weight gain. A person wanting to lose weight should do so in a scientific way for long term benefits. A healthy diet and regular exercise or incorporating yoga into your daily regime can help to lose weight. Eat more of green leafy vegetables, fruits and protein and less of fats, butter and potato etc. I suggest you to eat frequent small meals and eat lots of fruits and non-starchy green veggies, go slow on fats, eat carbohydrates in moderation and increase your protein intake .Get a diet chart made from a nutritionist. A calculative and disciplined approach will be helpful. Hope this helps.
Take care and regards!
If you want to reduce fat and keep it off, then it will take some time. I won't assurance 5-10 pounds weight loss in a week or two weeks’ time, but I will say you can reasonably reduce 1-2 pounds of body fat a week, and build muscle at the same rate. You can’t put the body weight on overnight instantaneously, and therefore it's not going to magically disappear overnight.
I HIGHLY recommend the paleo diet.. give it 30 days and you will see amazing results. It's eating healthy foods and cutting out problem foods that cause you to gain the weight to begin with. Any exercise will help when you eat this way. You don't have to count calories you eliminate the foods that cause the weight gain, the spikes in insulin which causes the weight gain and amazingly you will lose weight.. you will have more energy and it will become easier to exercise and you gain that energy.. I'm down 60 lbs and am loving eating this way.. it has cured a bunch of health problems and it has helped a bunch of people(including my parents) get to where they want to be with their weight.