For seniors, in particular, a regular lower body workout is critical for maintaining balance and strength. Falling is big risk as we age. You have probably seen the commercials and it's really no joke. Falling is dangerous.
Our lower body is the first line of defense against that risk. It stands to reason that we want a strong first line of defense. Keeping your legs, hips and lower backs strong will help you stay on your feet.
In addition, proper stretching before exercise and even before starting your day can help with balance and strength in your lower body. I will outline why you should work your lower body, along with how to do so.
I have answered part of this question above. To reiterate, because it's really important, a regular lower body workout increases bone density, improves your balance and stamina and decreases injuries to your knees and hips, along with your risk of falling.
Secondly, the lower body muscles are the largest in the body. As a result, they will burn the most fat when being worked. It is purely logical (very Spock-ish, huh), from an efficiency standpoint, to be sure to keep your lower body involved in your workout no matter how old you are.
The third reason is that a strong lower body will increase the likelihood that you will be able to stay active later in life. You will be able to climb stairs, mow the lawn (of course, you may choose to have the 15 year old next door do it for you), do general home maintenance, keep up on your golf or tennis game, etc. The lower body is our support system for activity. Without it, we mostly sit. That's no fun.
As with other muscle groups, there are a number of lower body workout exercises you can do to keep your lower body strong. For me, the two best exercises are squats and lunges. There are several variations for both of these exercises. In all of them, they strengthen almost every lower body muscle in one exercise; very efficient.
Squats - Basically, you start in the standing position with your feet shoulder width. Keeping your back straight, bend your knees until your thighs are parallel with the floor. Then, stand back up. That is one repetition (rep). Do 10-15 in a set. Rest for 15-30 seconds and do another set. Perform 3 to 5 sets depending on your fitness level. Start out with only your body weight until you get the form right. Then start adding weight with dumb bells, bar bells or kettle bells. You can also start out with one hand on a chair or counter top for balance. Here is a good video to help out.
Lunges - Lunges are similar to squats except that your legs are not doing the same motion at the same time. Think of lunges as "deep knee walking." Similar to squats, I recommend starting out with no weight to get the form right. That is important so you don't injure your back. Add weight by carrying weights in your hands hanging at your side. Use a similar rep & set strategy as with squats. Lunges can be done by stepping forward, to the side or backward. I use all 3 for variety. Here is a video.
A third exercise that I like and use as part of my warm-up is the standing bird dog. The best way to explain this is with a picture. It is great for balance and getting a stretch in your thighs. If you have ever hunted with a pointing dog, you understand the name of the exercise.
A lower body workout is critical for overall fitness and weight loss. Keep reading and keep building your weight loss program.