We do not recommend fasting from food if it is medically unsafe or unwise for you to do so. There are a number of reasons why this could be the case. If it is unsafe or unwise for you, please choose something other than food to abstain from.
For those who have recovered from an eating disorder or actively have a disordered relationship with food, we encourage you not to fast from food and to consult your medical provider. The eating disorder part of someone in recovery's brain can take something good—fasting, which is an important spiritual discipline—and distort it into something harmful. Recovery can be slow and relapses can happen, so if that is you, we encourage you to fast from something other than food.
What we've learned is that for individuals who have or who are currently struggling with eating disorders, fasting from food fuels the problem which has its roots in control. The person in recovery or maintaining recovery has to depend on the Lord to eat—the opposite of those who fast. Eating is the choice to trust in God and the way he designed our bodies. When we fuel our bodies, we choose to trust in God as creator, not in ourselves and what we want our bodies to be like.
Here is a very helpful podcast episode on all of this.