You want to weigh a specific number on the scale. But healthy weight and actual weight are NOT the same.
Healthiest to be lean, and measuring lean body weight is not possible on the scale. How lean you should be to be healthy is also determined by your genetic make up
Healthy weight, healthy specifically lean, both chance relative to weight changes; and weight maintenance.
Health relative to waist (under 35 for women, and under 31 for men, possibly more accurate than standing on the scale.
Healthy waist to hip ratio: for women .85 or less, for men 1.0 or slightly greater.
Your healthiest weight for your age and sex is the weight you should maintain to maintain the health of your metabolism and the weight at which you are least likely to get ill. So your healthiest weight is the one with the least likelihood of illness like diabetes or cancer or death. Knowing exactly what weight this is for you is a bit trickier to figure out and has to be discussed with your health care provider.
Small weight changes make a difference, as individuals slowly creep up their risk of metabolic syndrome increases.