Do not, however, focus on weight or food. These are only symptoms of whatever the real problem is. Do not give the person guilt, threaten, punish, bribe or preach. He does not need to make a suggestion of what the medical problem is but only point out how she may have changed. If her work performance is affected, you should consider discussing this, with clear communication about her behaviors that seem affected by weight loss.
Patients feel controlled, intruded upon, or ashamed when confronted about their eating disorder.
A very caring, non-judgemental approach is necessary. You can validate their position while also stating yours. Their denial does not mean that your words were not effective. She will take them in and mull them over when she feels safe. This might be less complicated because they do not have supervisory power over her.