Another common question that I get asked on a fairly regular basis "What should I weigh?" Of course the mere phrasing of the question implies that if you fall short of some particular "ideal" then you may be flawed in character as well as body. What I would prefer is that we would someday ask, "Am I at a healthy weight for me?" or "Is my percent body fat in a healthy range?" or even "Does my body fat put me more at risk for certain health conditions?" The last few phrases are more suggestive of each individual looking at his or her state of health based on more than one factor versus us all trying to measure up to a particular standard. But since old habits, and old questions, die hard, here are a few questions that you might want to ask yourself first.
First of all, ask yourself "What was the last weight I felt good at?" Don't worry about any charts, etc at this point. It might be five pounds less, it might be fifty, but this is one of the first steps in looking at you as an individual. Next, ask yourself if you think that is a realistic weight. Have you had a few birthday's since then? Do you have to take medications (for now anyway) that might keep you from losing weight? Third, ask yourself honestly if you are willing to do the work, yes I said work, involved in getting to a particular weight. And remember it's not just work to get to that weight, it's work to keep it off as well.
Now as far as something that has more hard science to it, there are some other ways to assess your health risk. First of all, when looking at yourself, you shouldn't use the Body Mass Index (BMI). Yes, you read that correctly. Why not? Well, this three year old article written in Slate gives a great history of BMI and contains a critical phrase: "The cheap and easy BMI test allowed them to plan and execute ambitious
new studies involving hundreds of thousands of participants and to go
back through troves of historical height and weight data and estimate
levels of obesity in previous decades." In other words, the BMI is only useful when doing an overview of populations for research purposes or to implement as a screening tool, but not to make clinical judgements on individual health. For example, let's say a University is recruiting people for a study, and one of the criterion is that participants be obese. This happens to be a study where participants will receive some monetary compensation for their participation, so the researchers get flooded with applicants. Because of time constraints, and funding constraints, the researchers need to do some "weeding." (aka screening) One of the easiest ways to "weed" out non-overweight or obese individuals is to look at their BMI. So, in this case, the BMI had a legitimate use as a reasearch/screening tool as no judgements were made.
So, if your physician or another health care person makes a comment about your BMI and tells you that it's high/low or good/bad, etc, you can tell him/her that that was an inappropriate use of that tool. What you need to do is whip out your tape measure and have them do a Waist-to-Hip Ratio (WHR). If you are equipped with a smartphone and/or the health care person has internet, you can even whip out the Wikipedia article on where to do the measurement, and also charts on risk assessment. This is a better health risk assessment based on where you might be carrying your excess adipose (fatty) tissue, and relatively easy to perform even if it is more "hands on." (Link). Occasionally you might even find a physician and/or Registered Dietitian that has been specially trained in measuring body fat percentage using skinfold calipers, but I've seen that more commonly used by personal trainers at gyms. If you are lucky enough to be associated with a university you might even witness or get to participate in hydrostatic weighing.
Once you've done your WHR or body fat assessment, if you are in the high risk and/or high body fat percentage, you probably still have a weight loss goal in your mind. Keep in mind there is evidence that losing just 7-10% of your excess weight shows benefits in lowering obesity-associated health risks (Link). No reason why you shouldn't aim for lower, if it improves your health status, but sometimes a lower short term goal might seem more attainable and realistic.
Take home message--use methods meant to be tailored to individuals when looking at your weight loss goals.