It is doomed to fail.
The only types of diet that can dip that low in calories while still being safe are ones that work on the pancreatic function. In short, if you have the amount of protein your body needs to maintain muscle mass, and very little carbs, then your body will go into a state of Ketosis. This is the principle behind the Get Shredded diet, the Atkins diet, the Ideal Protein diet, and the Lindora diet. In ketosis, the following things happen:
- Your pancreas stops producing insulin, and starts producing glucogon (a fat burning hormone)
- The balance of the calories your body needs to function come from your fat stores
- Your liver and kidneys produce a higher amount of ketones (part of ketosis) which limit the amount of proteins your body can process (i.e. you need a bit more protein than normal) and also help convert fat to energy.
- It is near impossible to get <400 Calories eating protein sources (it will be closer to 900-1200 Calories)
- Exercise during a diet like this should be low-heart rate (zone 1), which burns much more fat than sugar.
Understand that a no-carb diet is not sustainable forever, and increases the load on your liver and kidneys. At most, 3-4 months.
The problems with the diet you proposed
- You still have carbs/sugars in your diet, which means your pancreas is producing insulin and not glucogon. I.e. your body is working off of sugar, not fat
- Due to the intense starvation, your body will cannibalize its own muscle and organs (which you need both to burn fat and to live) to deal with the starvation
- Also due to the intense starvation, your body will hold on to its fat stores all the more tenaciously.
- When your brain doesn't get the blood-sugar it needs, you become irritable, mean, and in severe cases you start to hallucinate. You will have no energy, and couldn't work out if you wanted.
- It is an anorexic diet which the body will do all the things listed above even quicker.