BMR

BMR is the number of calories your body needs a day to meet energy needs of your organs and such.

First problem with eating below BMR is that it SIGNIFICANTLY increases the likelihood of becoming malnourished. If this happens, your weight loss can stop.

Second problem is that your body is a VERY smart thing, it tries to ensure it always has enough for the organs. Eating too few calories can cause the body to reduce it's energy expenditure significantly, upwards for 60% in some cases. That is a MASSIVE drop in calories out, which at times can completely offset the lack of food, causing a stall or even weight gain (ironic!).

This does not mean you can't go a day or two under BMR. That is fine and normal. The issue is prolonged periods of eating under BMR can cause issues.

Which website is more accurate in calulating your BMR?

None really. All are pretty close to each other.

The best way to calculate BMR is medically. Some gyms can do this, and some doctor offices can.

Generally, the best bet is to use a website to calculate BMR and TDEE. TDEE is your total daily energy expenditure. It is the energy you spend on a daily basis such as walking, sitting, breathing, eating, brushing your teeth etc. It includes BMR.

So, the goal is eat under your TDEE, and above your BMR.

My BMR is 1708 and my TDEE is 2050. A 20% decrease from my TDEE in calories is 1640 (should lose a pound a week this way). I will be below my BMR...is that ok?