First, your body eats everything before it will affect your heart, so no worries there. You can certainly do 40 day fast with water. People who actually drink coffee and tea during a fast are the ones who pay. Caffeine is diuretic and takes water out of the body, also partial feeding leads to starvation. Just do water and nothing goes in your mouth, no tooth paste, chewing gum, salt, etc.
Now I do see a few problems in your plan. With a very long fast you need to have at least same number of days to feed your body and build nutritional reserves, but I recommend 1.5 X number of days fasted. 7 days between 40 day fasts is rather short period to refeed your body.
Secondly, you can not expect to Water Fast and then lose weight and keep it off. It is about changing your lifestyle. If you want to lose weight eat plant based diet, juice (freshly squeezed, organic fruits or vegetables only) for as long as you can, fast intermittently and then stay on plant based diet. Self control is crucial when you talk about losing weight and keeping it off. Look what you did after eating good for seven days and ate a Borito.
If you want to lose weight, stop eating SUGAR, meat, dairy, grains and all processed foods. You may ask what about proteins? I say what does elephant eat? How does it get protein? All living foods have protein, leaves, nuts, seeds, legumes, beans, etc.
I hope you do things gently, it took years of abuse to be where your are, it will take years to be where you want to be.