Try national eating disorders association.com
The Overload Principle is focused on sports fitness training.
It states that athletes must work harder than they usually workout as their bodies adjust themselves to higher workouts.
To safely apply Overload to your workout you should monitor the intensity of training as you increase it gradually and progressively.
You should choose and plan over one type of workout to apply Overload on it.
All other training activities should be coordinated and adjusted preventing other factors that influence overloading in duration and volume of training.
I found some tips and resources from CDC. Hopefully they're helpful:
https://www.cdc.gov/obesity/strategies/index.html
https://www.cdc.gov/obesity/index.html
Low self image could be caused by bullying, just overall not liking yourself or other things. Low self-image can cause depression, anxiety, eating disorders and other things that are harmful to you and your body.