Muscle mass weights twice the amount of fats. and thats a fact.
In order to lose weight you need to burn a whole lot more.

For overweight person, my suggestion is non impact workout. In order to lose weight and size.
For eg. Swimming or cycling. If one is over weight u r not suggested to do running or anything that impacts your knees, hips etc etc.

Key point 1 is to raise your metabolic rate. by doing so u need to do more cardio workout. cardio workout could well means go for swiming or others means.
Start a day or 2 in a week then follow up by more days. you will see immediate effect like tightening of your arms and legs. But dont go celebrating yet.
Your goal must be set like for eg. i want to lap a few rounds today.
complete the goal in the time u think suitable for you.
In any plans to cut down weight or size must be measurable. That means for eg. waist size, chest size, biceps size.
Plan your minor goals like" i want to have a 34 inchwaist by June."
I wan my biceps a size 40, etc etc.

If you have a goal then you can do it. BE DISCIPLINE AS WELL!

As for diet for those who wan to cut down size .

i share my diet plan,

[WEEKDAYS/WORKING]
morning,
milk a glass, cereal/oats
high fibre content fruits

Lunch
minimal rice, chicken,
fruits and vegetables
coffee
*note that coffee(caffeine) will kill vitamin c but will give u a boost of energy for workout sessions.

[workout]

Dinner
minimal rice/wholemeal bread,egg,vege,fruits
fruit juice.

[WEEKENDS/OFFDAYS]

breakfast
eggs,milk,fruits,bread

[workout]

lunch
rice,fish/chicken,vege,fruits

[rest]

[workout]*only if u r well rested

dinner
tuna w/ bread, fruits, vege

*strictly no dressing for salads, no syrup wit your juices.
*eat snacks like nuts in between if u feel hungry

i crafted this regime in order to stay healthy n fit not to have washboard abs nor run like some baywatch actor.
when u have achieved ideal BMI, u can start goin for more vigourous activity, eg, rock climbing, mountain hiking, biking,. this will maitain your metabolic rate or increase.
* note that as u get used to the regime you will consume more but only your intake grow in proportionate to your exercise.