28/F/5'8 - CW:175 | GW: 150 - Calorie Intake Questions

IMO, 10 pounds in two months is too fast for someone who isn't severely obese . . . which you aren't.

If you are very healthy, tend to have very resilient health, have virtually no other sources of stress (physical or psychological) in your life, are getting truly excellent nutrition . . . you might be able to keep it up for 2 months (i.e., short limited time) without negative health consequences, fatigue/weakness, appearance issues like hair loss (which is usually delayed, i.e., shows up a few weeks later.

The risk of compensatory over-eating episodes, or giving up entirely because of being unsustainably aggressive - those are still in the potential, too, but going white-knuckled will power focused extreme for two months (quite limited time) might be more possible than trying to stick with it for the long haul to lose more weight.

I'd put a higher level of concern on health risks.

For me, resilience was one of the few things that truly declined as I aged; I'd feel more optimistic about your proposed approach if you were 19-20, for that reason, but in practice it's more individual than just age. Besides, 28 is far from over the hill (speaking from a personal perspective of being 66 myself).

A common recommendation around here, as a rule of thumb, is to lose no more than 0.5%-1% of current weight per week, with a bias toward the lower end of that for lower health risk. For you, that would be 0.875 to 1.7. Another alternative rule of thumb is to cut no more than 20% from your TDEE to get a calorie goal, and less of a cut preferred if for less major weight loss (such as yours).

When you ask about your activity level, there's a definitional issue. MFP is designed with the intention that you would set your activity level based on your activity level NOT including intentional exercise. Based on that, MFP will give you an estimated calorie goal before exercise that includes the targeted weight loss. It then expects you to log your exercise when it occurs (or synch a good tracker**), and eat those calories, too, keeping the same calorie deficit for the same weight loss rate. You would then eat different numbers of calories on exercise days vs. non-exercise days.

(Apple's is a good tracker, but they way Apple's interfaced it to MFP deviates from the MFP specs, so doesn't work correctly for some/many cases. There are ways to make it work better.)

If you don't want to do varying calorie levels, but prefer to eat the same number of calories every day, IMO it would be a good idea for you to use an outside TDEE (total daily energy expenditure) calculator to estimate your calorie needs. These average in your planned exercise to provide a standard daily calorie level that applies on exercise days or non-exercise days. Because they're designed with different underlying assumptions, they tend to use different activity level multipliers.

If you want to do that, I think this is one of the better calculators (really estimator, like all of them, including MFP):

https://www.sailrabbit.com/bmr/

I like that one because it has lots of different activity level options, with relatively good descriptions for each. It also lets you compare several research-based calorie needs estimating formulas. That does mean that its user interface is complicated and possibly more confusing than some others, at first glance. Simplicity isn't always better.

The underlying issue here is that researchers believe that the body can only burn a certain amount of fat per day per pound we have on our body. When we burn more than that, the body is likely to down-regulate the more optional processes (like hair growth, energy level, body temperature, etc.), or to burn useful tissues (like muscle) in addition to fat. The former can make a person lose slower than expected at a given calorie level, or to subtly (we hope it's subtle!) decline in health.

The reason I mentioned stress up front is that a calorie deficit is unquestionably a physical stress, and the bigger the deficit, the larger that effect. The effect of stress on our bodies - even "good stress" like exercise - is cumulative, including both physical and psychological stressors. If the rest of one's life is more stressful, adding a big calorie deficit and/or hearty new exercise can have worse consequences than it might for someone with an otherwise low-stress life. (When I type "consequences", I mean health risks again, such as reduced immune system function, as well as potential for negative mood impacts, including "hanger" that affects personal relationships and life happiness.)

Is any bad thing guaranteed to happen, from losing quite fast? Of course not. But risks go up.

I lost too fast at first accidentally after joining MFP, because I'm the quite unusual case of someone whose calorie needs it significantly UNDERestimates. I was eating 1200 plus all exercise calories, so more like 1400-1700 gross calories, in context of a pretty low-stress life (retired, didn't increase exercise, healthy, good nutrition, etc.). Even though I corrected quickly, I got weak and fatigued, then took several weeks to recover. No one needs that.