eat less calories than recommended not losing

If you're not netting at LEAST 1200 calories a day, it would account for the lack of weight loss. If you are not fueling your body properly it will hold on to the fat for fear of starving, causing a lack of loss and sometimes a gain. Sometimes you have to eat more to lose more... I know it sounds stupid but it is very true and has been proven time and time and time again. Sodium could also be a culprit...

Yes, texas... that number is the lowest MFP goes for a reason. If you eat less than that, you risk doing serious and possible irreversible harm to your body and metabolism.

Are you religiously recording everything you're consuming, beer and all? If not, try doing that - you might be surprised. Booze has tons of calories.

The other thing to keep in mind is this: I read several years ago that to lose a pound of body weight you need to expend 3,600 more calories more than you consume in a given time period and this has been confirmed by several credible sources over the years. This means that if you are consuming 100 calories less than your target every day, it's going to take you 36 days to lose one pound!

I've lost 9 pounds in about three weeks, but I've been exercising like crazy and keeping the food intake well below what MFP says should be my daily limit - as a result, most days my caloric deficit - how many calories I burn minus how many I ingest - is in the range of 500 - 1000 calories or even more.

Given that measuring caloric intake and consumption are very inexact sciences, I very strongly believe that you will never lose weight if you're only 100 or so calories below your limit.

It's not necessarily bad to eat under the 1200 calorie recommendation. However, if it's consistently done for an extended period of time, you're more likely to gain weight rather than to lose because your body will go into that starvation mode. If you eat under the 1200 recommendation sporadically, it shouldn't be a problem.

Another thing to keep in mind is that you need to eat a minimum of 1200 NET calories. That means if you are eating 1200 calories, but burning 500 calories when you exercise, you are only consuming 700 net calories and your body will go into starvation mode.

You have to be spot on with your food intake. I used MFP for the first 6 months without losing because I was also a "weekend warrior". You will NOT lose weight continuing this behavior and have to make the choice between that and your weight loss goals.
On an up note you can imbibe once you have reached your goal sometimes without fear of gaining, it is much easier to maintain but you really have to be dedicated to getting there first.
I have found that diet is about 85% of the battle. Unless you are consistent here you will not see the results you want. I actually had to increase my food because I was not eating enough so those calories are very important to monitor.

I'm going to point out the other factor in the weight increase. Beer. I gain anytime I drink beer whether it is just one or a few. It's just not good for weight loss... period. Wine does the same thing for me.

First of all, if you are eating under 1200 calories a day, you could be starving yourself. When your body is starving, it tries to CONSERVE FAT. So make sure you up your intake. Second, you should be logging everything with calories that you consume, including alcohol. If you're looking for a low cal alcoholic beverage, I would recommend liquor + diet soda. Beer and wine are also okay, but remember to plan ahead for these things. They *do* count in your intake.

ETA: When your body is starving, not only does it conserve fat, but it burns muscle--that includes visceral muscle, such as your heart. That's why this is such a dangerous plan.

You have to be spot on with your food intake. I used MFP for the first 6 months without losing because I was also a "weekend warrior". You will NOT lose weight continuing this behavior and have to make the choice between that and your weight loss goals.
On an up note you can imbibe once you have reached your goal sometimes without fear of gaining, it is much easier to maintain but you really have to be dedicated to getting there first.
I have found that diet is about 85% of the battle. Unless you are consistent here you will not see the results you want. I actually had to increase my food because I was not eating enough so those calories are very important to monitor.

I completely agree with this. Once you are at a maintaining point it's not a big deal if you have booze (in moderation) on the weekend, but if you are serious about the weight loss you either need to cut it out completely or try to limit yourself to one or two because that can completely stall you even if you are good with your diet during the week. Alcohol (especially beer) has a LOTTTT of calories.

I am a huge beer fan and since I started my diet I limit myself to one or two every 2 weeks or so without any bad results so I can have like a "mental" day without having to be so strict. But I still always log it!

Several really good posts here. MFP accounts for average daily consumption based on average activity levels for each user. This is the inexact part.

Jumping right to starvation mode. The 1,200 Calorie threshold is also inexact. Based on hormonal response, normal activity levels, and genetics, your body enters starvation mode when it experiences a deficit for more than 24 hours. For example, you consume 1100 Calories for two days, and you're there. Your body triggers a response to conserve precious fats, which store around 9 Calories per gram of fat and nonselectively catabolize proteins, i.e. muscle, which only account for about 4 Calories of enery per gram. The reason is your body has determined that all that muscle is nonessential to survival, and from that standpoint, your body is right. Your body will catabolize muscle nearly exclusively until you have lost so much muscle that you can't perform your normal survival activities, and then it will begin to catabolize fat and mucle until you eventually die of starvation. That sounds bad, and it is. It has already been mentioned by Katie that your heart is a muscle. Indeed, your body doesn't care, and strips heart muscle.

Now, if you are just looking to drop pounds, it will cost your health if you aren't careful. You really need to ensure you stay above the starvation mode. If you are looking to burn off fat, there are a couple points to consider, as well. Your body maintains around 30 minutes of glucose reserve from your last meal. Fat metabolism occurs slower than muscle metabolism, and slower again than glucose metabolism. Under high demands, i.e a cross-fit, Gym Jones, true sprint workouts, you will first burn off all your glucose reserves. No fat is metabolized while your body has a glucose reserve. Additionally, your brain operates better when running off glucose v. ketones and aldehydes. So that big exam really needs glucose for you to mentally perform at your peak, though the signals themselves travel fine regardless, just not at their max efficiency. No glucose=fat burn at low demands.

After about 30 minutes, your glucose reserves will be depleted and only then will your body begin to metabolize fats into ketones and aldehydes, substituting for glucose, when the energy demand signal is lower. Somewhere around 140 heart rate as an inexact measure of a 35 year old, your body's energy needs exceed that which can be provided by the slower fat metabolism, so your body again nonselectively catabolized muscle. If you were truly dedicated to getting a more exact moment when you body runs out of glucose, you could buy a glucose monitor, run for 30 minutes, and take your blood sugars every couple minutes into the run thereafter to see the exact point that your body has run out of glucose and you need to downshift your activity so you are only burning fat. This would be a real interesting experiment. Based on your results, you can back off the hard cardio a few minutes before you blood sugars measure a drop and really tailor your workouts to positively effect body composition. Probably more than you want to do, so 30 minutes is a good estimate.

Here's the rundown. Your Caloric intake is too low and your body is in starvation mode. You are likely losing muscle mass and your heart health is permanently at risk. Your personal metabolism has also dropped, making the MFP overestimate your average daily expenditures and weight loss. Any exercise you do while starving yourself will further the breakdown of muscle and conservation of fat. This will adversely effect your body composition even if you start to lose weight. Basic assumption is you want to drop fat, not muscle. Don't believe the hype that if you strength train for 30 minutes a few times a week you are going to look like Lou Ferrigno next month. That's the result of 8 hours a day for 10 years.

The way ahead. Ensure you are intaking at least 1,200 Calories a day, to include alcohols. Alcohols provide approximately 7 Calories per gram, and while not a protein, fat, or carb, you body metabolizes alcohols as if it were fat. Not a big deal as long as you account for it. MFP has every hard liquor I drink, so its not a problem (I do recommend the effect of a nice drink at the end of a workout when you are a little dehydrated ... very nice). When you begin your workouts, go hard the first 30 minutes to burn off glucose reserves, then finish light for the next 15-30. This will ensure that the major percentage of Calories burned are fat Calories. Don't misunderstand, you will burn more fat by going hard throughout, but you will also be burning muscle. If you were to walk for 30 minutes after a meal, you will indeed burn off some of the glucose, but not all of it, and your body will replace the glucose from your meal before it ever touches fat reserves. Pro athletes consume energy pastes during their workouts to provide their bodies with more glucose so this doesn't happen and they can maintain high levels without losing muscle. I'm certain Tom (TAWoody) can go into consumption of protein or energy drinks during workouts if you were training up for something. Sorry Tom if I threw you under the bus, you look like this is your bag. As a species, we survived by selecting for individuals who could best store fat. Great for hunters and gatherers, not great for the beach.

Net Calories is a simplification to show you the effect of what you eat minus what you expend. This isn't directly related to starvation mode, but gross Calories are. You will notice the warning if you have eaten less than 1,200 Calories when you submit your food log. As long as you are intaking at least 1,200 gross Calories, you can exercise it all off and there isn't that warning. Weight loss is strictly thermodynamics, but body composition is more complicated. MFP calculates your net Calories minus an estimate of your daily activity expenditure to determine what you stand to lose weekly.

Last downside here is the alcohol. On average, a shot of alcohol has around 102 Calories, about the same as Coors Light. For Coors Light at 4.2% (*12 oz) you get an alcohol effectiveness of .504 (content times volume) for each beer plus all the water bloat. A shot of 80 proof is 40% (*1.5 oz) for an alcohol effectiveness of .6 without the water bloat. So, Calorically, you are better off with 5 shots at about 510 Calories v. 6 Coors Light at about 600 Calories. If you are drinking to be social, go with the super light 55 Calorie beers, and make sure you add it to your journal. I mix my 3 shots of whisky with a splash of the 5 Calorie tea at home at the end of the workout, and by the time I finish the shower, everything in the universe is right again.

Please make sure you are taking a daily multivitamin and calcium supplement. If you are a milk drinker, consider AlmondMilk, far less Calories, more calcium, and very tasty. If you are interested in a discussion of the importance of calcium, osteoclasts, and osteoblasts, we can go down that road, but in short, a multivitamin and calcium supplement will cover you. I'm touching on a lot of bases here, but it's really not too complicated once you know how to go about it. Don't get overwhelmed, you're in this for the long haul, and there are plenty of us here to support.

Again, 1,200 minimum intake including alcohols (shoot for a bit hgher-it's difficult to get adequate nutrition at low levels and alcohol only offers mental nutrition at best), 30 minutes harder cardio (140+ heart rate) followed by 15 or more minutes light cardio a few times a week , a multivitamin, calcium supplement, and you will start making headway toward your goals. Don't forget stuff like mowing the lawn burns a few hundred Calories for that hour behind the push-mower! If you are uncertain of your ability to begin new workout routine, I really insist you get checked by a physician for a physical exam and seek guidance from a nutritionist. All this advice is worth what it cost you. In the end, it's your health, and we want you to succeed. If you intake 1,400 Calories and burn off an additional 450, you are doing great. It's an ego-hit, but change the settings for your activity level. I sit behind a desk now, too.

Best wishes and have a great weekend!