How can I convince my mum to let me lose weight ??

Excellent Weight range indicator, BMI, and more, calculator - gives you:

BMI – Body Mass Index BMI is used to find out if a person is underweight, normal weight, overweight, or obese Waist-to-Height Ratio Body shape (determined by Waist-to-Height Ratio) is often considered to be the best indicator of health related to weight. RMR – Resting Metabolic Rate The number of calories you burn if you do nothing all day. Healthy Body Weight RangeThe range with the least risk of weight-related health problems. Daily Caloric Intake The recommended number of calories from food/drinks to meet your weight goals. Target Heart Rate The heart rate needed to achieve maximum exercise results.

http://www.webmd.com/diet/calc-bmi-plus?ecd=wnl_day_123008

Take care and Happy New Year !!