How to Lose Weight - The Basics of Weight Loss

At it's most basic, losing weight is about burning more calories than you eat. That seems
simple enough, but if were really that simple, none of us would have a weight problem. Too
often we take drastic measures to see results -- diets, pills or those weird fitness gadgets on 
infomercials that promise instant success. Maybe you lose weight but what happens when you go off that diet or stop that crazy workout program? You gain it all back and more. The real secret to weight loss is to make small, lasting changes. The key is to forget about instant results and settle in for the long run.
Rules of Weight Loss
To lose one pound of fat, you must burn approximately 3500 calories over and above what you already burn doing daily activities. That sounds like a lot of calories and you certainly wouldn't want to try to burn 3500 calories in one day. However, by taking it step-by-step, you can determine just what you need to do each day to burn or cut out those extra calories. Below is a step by step process for getting started.

1. Calculate your BMR (basal metabolic rate). Your BMR is the amount of calories your body needs to maintain basic bodily functions like breathing and digestion. This is the minimum number of calories you need to eat each day. Keep in mind that no calculator will be 100% accurate, so you may need to adjust these numbers as you learn more about your own metabolism.
2. Calculate your activity level. For a week or so, keep an activity journal and use a calorie calculator to figure out how many calories you burn while sitting, standing, exercising, lifting weights, etc. throughout the day. Another, easier option is to wear a heart rate monitor that calculates calories burned. After a week, add your totals for each day and average them out to get a general idea of how many calories you burn each day.
3. Keep track of how many calories you eat. For at least a week, enter and track your calories online (e.g., with Calorie Count) or use a food journal to write down what you eat and drink each day. Be as accurate as possible, measuring when you need to or looking up nutritional information for restaurants, if you eat out. After a week, add your totals for each day and average them out to get a general idea of how many calories you eat each day.
4. Add it up. Take your BMR number and add your activity calories. Then subtract your food calories from that total. If you're eating more than your BMR + your activity calories, you're at risk for gaining weight.

Example:
Mary's BMR is 1400 calories and she burns 900 calories with regular exercise, walking around and doing household chores. To maintain her weight, she should be eating 2300 calories (1400 + 900= 2300). However, after keeping a food journal, Mary finds that she's eating 2550 calories every day. By eating 250 more calories than her body needs, Mary will gain about a pound every 2-3 weeks.
This example shows how easy it is to gain weight without even knowing it. However, it's also easy to lose weight, even if the process itself can be slow. You can start by making small changes in your diet and activity levels and immediately start burning more calories than you're eating. If you can find a way to burn an extra 200 to 500 calories most days of the week with both exercise and diet, you're on the right track. Try these ideas:

Instead of...	Do this...
An afternoon Coke	Drink a glass of water. (calories saved: 97)
An Egg McMuffin	Eat a small whole wheat bagel +1 Tbsp of peanut butter (calories saved: 185)
Using your break eat sweets	Walk up and down a flight of stairs for 10 minutes (calories burned: 100)
Hitting the snooze button	Get up 10 minutes early and go for a brisk walk (calories burned: 100)
Watching TV after work	Do 10 minutes of yoga (calories burned: 50)

Total Calories Saved: 532 (based on a 140-pound person) How Much Exercise Do I Need?
Exercise is an important weight loss tool, but how much you need varies from person to person. The guidelines recommend at least 250 minutes per week, which comes out to about 50 minutes, 5 days a week. If you're a beginner, start small, for example with 3 days of cardio for 15-30 minutes, gradually adding time each week to give your body time to adapt. Learn more about getting in shape and getting started with exercise.
_Source:
Donnelly, J.; Blair, S.; Jakicic, J.; et al. Appropriate Physical Activity Intervention Strategies for Weight Loss and Prevention of Weight Regain for Adults. Med & Sci in Sports & Ex: Feb,