Hi Insha
Body is a great keyword. But maybe putting the luck of 7 aside and creating the vision of 7 as the amount of days in the week. An idea to develop this would be how to maintain or get your perfect body by doing certain things each day of the week (exercise/diet plans for 7 days - even if 1 day is a rest day, it's still a part of the program)
Body7 probably does roll off the tongue a bit better but it all depends on how you develop and promote 7Body.
The positives are that its short and there can be a link between the number and the word. Can't see a value yet because it needs the development and promotion.
What do other NamePros think?