Fact 1: Whether you lose weight or not depends almost entirely on whether you’re eating less calories than you need to maintain your weight. The number of calories needed to maintain your weight depends on your metabolism. Eating less calories than you need is called ‘calorie deficit.’
Example 1: If Jill has a 1500 calorie a day metabolism, then eating less than 1500 calories a day will usually make Jill lose weight, and eating more than 1500 calories a day will make Jill gain weight. If Jill eats 1200 calories in a day, Jill will have a 300 calorie deficit.
Fact 2: Your body has two main sources of stored energy; fat and glycogen. Glycogen is a form of carbohydrate, and it provides four calories per gram. It also soaks up more than its own weight in water. When you first start cutting calories (or carbs), you will consume your glycogen stores and they will steadily be diminished. This will cause rapid weight loss – which will continue for a few days (or over a week if you’re only cutting calories slightly). This rapid weight loss will give you a buzz of satisfaction – but very little actual body fat will be lost during this phase.
Example 2: If Jack weighs 75 kg and has a 2500 calorie a day metabolism, and his body has 500 grams of stored glycogen, and Jack cuts down to 1500 calories a day, then Jack will consume all of his glycogen stores within two days and lose 500 grams of stored carbohydrates and about a kilogram of water. After two days on diet, Jack will be down to 73.5 kg. But Jack will have just as much body fat as when he started, and when he starts eating more and his glycogen stores recover, he’ll put those 1.5 kg back on as soon as he’s gone 2000 calories over his maintenance intake.
Fact 3: Every kilogram of body fat has about 7700 calories. In other words, you have to burn 7700 calories more than you eat to lose a kilogram of body fat. And once your glycogen stores are eliminated, body fat will be your primary fuel source. This will make weight loss excruciatingly slow for people who expect the same results during prolonged dieting that they expected during the initial phase.
Example 3: Jack is still eating 1500 calories a day and is having a 1000 calorie a day deficit because he needs 1000 more to maintain. He’s eating 40% less food than he needs. But it’s going to take Jack nearly 8 days to get from 73.5 kg down to 72.5 kg, because that’s how long it will take for his 1000 calorie a day deficit to add up to 7700. Jack is only going to lose 130 grams of fat a day.
Fact 4: Most nutritionists recommend a calorie intake of 2000 a day for females and 2500 a day for males. This is arbitrary and based on averages; your need may be lower or higher.
Example 4: Jez has an eating disorder and regularly posts on MPA. Jez has a 4000 calorie a day metabolism, for reasons which he has never been able to ascertain, but he loses weight on anything less than 3700 a day and usually takes about 4300+ a day to gain anything. Jez burns 1500 calories a day more than an average adult male. However, Jez’s girlfriend only has a 1200 calorie a day metabolism, eats much smaller meals than he does, and burns 800 calories a day less than an average adult female. Both are atypical, but prove that there are extreme ends of both scales.
Fact 5: Once your glycogen deposits are depleted and it takes a 770 calorie deficit to lose 100 grams of fat, water and poop weight have more of an effect on your daily scale results than how much or how little you’re eating.
Example 5: Jane has a 1700 calorie a day metabolism, and she only ate 550 calories yesterday. She lost 150 grams of body fat, but drank about 200 grams more water than she peed out before weighing herself this morning. She also didn’t poop today, and has about 100 grams of poop in her digestive tract. So even after starving all day yesterday, Jane weighs 150 grams more on the scale. She is incredibly disappointed, and starts a thread on MPA asking what’s wrong.
Fact 6: Once you’ve depleted your fat stores, your body has one last ditch energy source to keep itself from shutting down; the protein that makes up your muscles and internal organs. This protein provides about 4 calories per gram – processed inefficiently – and carries water with it. At this point, weight loss once again becomes rapid and body tissues begin to waste away very quickly. Death usually occurs within a week or two unless calorie deficit ceases.
Example 6: Karen suffers from anorexia nervosa. Karen has a 1000 calorie a day metabolism, and is unable to eat due to the severity of her eating disorder. Karen ran out of stored fat tissue a week ago, and to provide her 1000 calories a day she has had to metabolise 250 grams a day of her own muscles and vital organs. Karen died today of heart failure because the tissues that made up her cardiac had been digested in lieu of food.
Please apply some of this information to your diets, avoid making too many unnecessary tip threads and consider the effects of long term starvation.