Hi, I've been on a diet for the past 2 weeks and I did not lose a single pound. I eat 800-900 calories daily and I run 5-6 miles every morning. Then, I saw online that 1200 calories is the absolute min daily calorie requirement for the body, so my diet actually put my body in a starvation mode and made my metabolism slow down, instead of losing weight, my body clings on every bit of fat I consume.
I really want to lose 10 lb in a month, but based on the calorie system, it means that I need to eat 1200 everyday, but in order to lose 10lb in a month, I need a daily deficit of 1250, that is I'll have to burn 2400 everyday. That seems to be impossible. It's like running 30 miles. But then why can some people lose 10 lb in a month?
Am I calculating it wrong?
Is there any way to lose 10 lb in a month?
Thanks for reading this and please comment : )

What's your hight, weight, age, and sex?

Look up BMR... it's your base metabolic rate, meaning it is how many calories your body would burn if you were to lie in bed all day.

Well, lets look at the numbers...

To lose 10 lbs, you need to roughly have a defecit of 35000 calories over whatever time period you want to lose that 10 lbs in. So, for a month, that turns out to be a defecit of ~1200 calories per day.

A defecit means to eat less calories than your body needs to burn in a day - NOT burn more calories (through exercise) than you eat. As Matt posted, your BRM is the amount of calories your body burns just to survive, but you need to adjust for activity and exercise. A good estimate for how many calories your body burns in an average day is to multiply your bodyweight times 15, and create your defecit by eating less than that.

Now, to figure out if losing 10lbs per month is a realistic goal for you, take your current weight and multiply by 1% - a healthy amount of weight to lose is 1% of your weight every week. So for me, I'm currently flucuating ~310-320, so I can healthily lose 3.1-3.2lbs/week. Times 4 weeks in a month, and thats a potential FOR ME to lose 12-13 lbs this month.

That means, assuming I was just starting out, and had maintained my current weight for a long time, I would start out by trying to create a defecit of ~10500 calories per week (3*3500), or ~1500 per day, through a combination of diet and excercise.

Another check is to take you current weight and multiply by ~12-15 to figure out how many calories your body will burn on an average day - I use a smaller number because I sit at a desk all day, but I exercise 3 times a week, so some days I'll burn more. For me, that amounts to ~3800-4800 calories. To calculate how many calories you should eat to lose weight, you can multiply your weight by ~10. For me, thats ~3200 calories - but I know that if I eat 4000 calories a day, I will at worst not gain any weight (well, I probably would because I've gone through a long period of undereating, which my body adjusted to by slowing my metabolism *some*, but if my body were *normal* right now, I wouldn't)

Now, all that is nice to know, but I typically do things a little backwards, for a couple reasons. I typically moniter my weight loss, and use that to determine how big my defecit is. The reason I do this is because I'm coming off of a long period of undereating, so my body is burning less calories than it should be. I know this because I typically eat between 2000-3000 calories per day, and have been losing weight at a rate of ~3 lbs per week. That tells me the amount of calories my body needs to maintain is somewhere between 3500 and 4500, which is roughly 300 calories less than it should be. Could be more, could be less, and i'll never know for sure because I don't keep an accurate calorie count. Only a rough "in my head" count, and I let the scale tell me whether or not I'm being honest with myself.

Now that I've said all that, heres the short answer you were probably looking for:

If you weigh.....................You should lose no more than..............
125.................................5 lbs/mo.
150.................................6 lbs/mo.
200.................................8 lbs/mo.
250.................................10 lbs/mo.
300.................................12 lbs/mo.
350.................................14 lbs/mo.
400.................................16 lbs/mo.
450+...............................18+ lbs/mo.

So there you go... Don't take these numbers as written in stone, but at the start of every month, I consider how much I currently weigh, and use this chart to determine how much weight I should lose in a month. 90% of the time, I'll come up a pound or 2 short for 2 reasons - as you lose weight, the amount of weight you can lose in a month decreases, and the amount of calories need to decrease as well. For example, I'll lose weight slightly faster at 320, than I will at 310, than I will at 300, etc. Also, every 10 lbs you lose, you need to cut another 100-150 calories out of your diet, so until you make that cut, you'll lose weight slower.

Finally, make sure you're eating enough. Multiply your body weight times 10 and eat that many calories, and you will lose weight, regardless of whether you exercise a lot or not at all. (unless you're like me and have been severely undereating for a while). If you're running 5 miles a day, you might even want to go (your body weight) x 12 or more. And if you have been undereating - you probably have if you've been eating 1200 calories a day or less, combined with lots of running - then you should work on upping your calories to 10-12 x your body weight or more. Actually, it'd probably be better to up your calories to maintenance for a month or so. Your weight loss might stall or you might gain some weight in the process, but your body will thank you in a month or 2 when you're able to be eating more, feeling better, and still losing weight. "Maintenance" is just the term for eating as much as your body needs, or basically, eating to not lose or gain weight.

So... thats that. I write a lot, but its not all to complicated.

Everything MAR said.

It's really very simple. VERY simple. I'll use me as an example, but you can easily adapt the numbers for your own. I weigh 170. I use 14 calories per pound of bodyweight to figure out what my *maintenance* calories are. (Maintenance calories are what you eat if you want to stay the same weight.)

170 * 14 = 2380 calories

So to lose weight I need to eat less than that, right? To *healthily* lose weight, you should eat about 30% less. So for me:

2380 calories * 30% = 713 calories. So I should subtract 713 calories a day.

That means I eat 1667 calories per day.

So if you take the 713 calories per day that I'm not eating, and multiply that by 7 (days in a week) = 4991.

Multiply that by 4.3 (weeks in a month) = 21,461 calories I don't eat each month.

Divide that by 3500 (calories in a pound) = I can lose 6.2 lbs a month.

(And look - that number is right in line with what MAR posted above!)

If I want to increase that, I can add in more exercise. On the days I work out, I burn an additional 500 calories. So working out 4x a week, I burn another 2000 calories a week. If I add all that in, I can lose about 8.5 lbs a month.

NOW --- having said all of that, you have to realize that when you lose weight, you don't just lose fat. You also lose muscle and water. In order to lose healthily you really need to be adding weight lifting or body resistance work to your exercising in order to maintain your lean muscle. It'll help with the rate of FAT loss .. which is the important part.

very very helpful! Thank you ladies

Thank you guys!!!!!
You really cleared up the confustion : D
I forgot to add up the calorie that my body burns naturally by itself : )

There seem to be an awful lot of formulas and numbers flying around, but what you have to consider is that fat loss is such a complicated thing. It's not just about eating, or not eating, a certain amount of calories per day. It's not even just about caloric deficit. If it were that simple then you're eating those 800 to 900 calories per day would have done it.

You have to consider where those calories are coming from. For example, I could eat 4 or 5 doughnuts per day and have my 1200 daily calories covered. Does that mean I'm going to lose weight? More importantly, am I going to lose fat (which is what you're really after)?

Stick to consuming your prescribed amount of daily calories spread out throughout the day. I'm not saying to eat 6 small meals per day. That's just impractical for the average person, but try to spread them out evenly into anywhere between 3 to 6 meals. Eat plenty of raw veggies, some fruits, nuts, lean meats, and drink plenty of water. Get a good fish oil supplement too.

As for working out, weight training plus high intensity interval training has been proven to burn way more fat than your slow, steady state cardio (which is what you're doing when you run 5-6 miles per day). You want to build muscle with weight training, and burn fat with high intensity interval training.