Run 5km in 20 minutes 3 times per week.
Only eat between 6pm and bedtime.
Drink low fat milk before 6pm to keep the hunger pangs at bay.
Drink milkshakes after 6pm.
If you are hungry and look at your belly and see lots of fat, don't eat.
Your body can survive using the fat.
If you're not willing to exercise to heavy sweating point 3 times per week for the rest of your life
and only stuff yourself with food once per week
for the rest of your life
Forget about about getting slim and/or staying slim.
It takes a lot of will power and a lot of vanity.