How to minimise strength loss whilst not weight training
Eat the right food.
I've mentioned in other answers that fitness is the equal distribution of three major components- Fitness: A Three Legged Stool, comprised of Exercise/Diet/Rest. If one of these three components is off then the whole thing falls over. This is a great analogy, however, fitness and strength are not one in the same. I'm going to assume you're confused at this point, as you should be because it is a counter intuitive concept. The difference between strength and fitness is this:
Strength is the mechanical ability to perform work.
Fitness is the capacity at which you can perform work.
Maintaining strength and maintaining fitness have different requirements, and it is these differences that allow you to maintain strength/ reduce the diminishing of strength by nourishing your body.
Eating the right foods just requires an understanding of what constitutes right food. You need to eat high quality proteins, fats, and carbohydrates.
Good sources of protein are foods like fish (Salmon, and Sardines), Eggs, chicken, and beef. For your meats try and get organic and grass-fed if possible.
Good sources of fats are foods like olive oil (uncooked is best), coconut oil (uncooked), avocados, almonds, and butter.
Good sources of carbohydrates are foods like potatoes (all types), quinoa, brown rice, 100% whole grain macaroni, and various beans.
All of your meals should be a combination of these three macro ingredients. Mix in a good amount of fruits and vegetables (vitamins and minerals) and you'll have a great balanced diet that will be more conducive for maintaining strength.
That's pretty much it, I hope the best for you!