70 pounds in 9 months is probably doable *IF* you have that much excess weight to lose. Healthy, maintainable weight loss is usually about 1 to 2 pounds per week. 9 months is about 38 weeks (since there are more than 4 weeks in a typical month). At 2 pounds per week, that's 76 lbs.
That being said, you will often lose more weight quickly and then the weight loss will begin to slow down.
The solution is fairly simple. Eat less, eat better and move more.
Eat less - watch your portion sizes. If you read caloric values in foods, the portion size is often less than the average person would eat in a sitting.
Eat better - make better choices. Fresh cut veggies are a better snack than potato chips. Baked foods are generally better than fried foods. Small changes can make a big difference.
Move more - walk when you can, take the stairs when you can. Set up an exercise routine. That doesn't make you have to join a gym - there's plenty of exercise you can do at home, for free.