To lose weight, you must exercise excessively for more than thirty minutes... I would say an hour because your body uses the calories in you for the first 20-30 minutes and after that, starts using stored fat and protein. I would also NOT recommend eating so little. It's best to eat a few small meals throughout the day than any big meals. And if you are not consuming enough calories and nutrients, when you lose your weight and get back to normal eating, you will gain it all back and then some.
When losing weight, you want to change your lifestyle and keep it that way for the rest of your life if you want long-term results.
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