Find out the students goals, short term and long term. Assess their current training/level of fitness and regular diet (Without embarrassing them but getting themselves to be honest). Can then look at their BMI and use a Calorie calculator to gauge their personalised calorie Intake needed to grow, and work out a steady short term and long term plan - In which I can curate a workout plan for them to reach these goals in a healthy way in said agreed time frame!