Weight training?
I'm fairly new at this forum and haven't yet shared my personal weight loss story. I underwent by-pass surgery at the age of 41 at a weight of 456. I'm now 44 and have stayed between 220-225 (at 6-2) for over a year. I experienced a rapid weight loss based on good nutrition, eating habits, and a very aggressive physical activity program. I regularly run (treadmill & road), swim laps, boxing heavy bag, and primarily dumbbell free weights and some weight machines. The majority of people at my current fitness facility, and for the most part at any I have ever used (Golds Gym, etc), really have limited knowledge when it comes to the science of resistance training. When they do succeed at strength and/or muscle building, they don't do so to their fullest potential for the following reasons: (1) They over train by doing more than necessary and not allowing for full recovery time between workouts. This is especially true for both men and women as they age (at 44 I don't recover as quickly as I did at 20. (2) In addition to doing too many reps and sets, they use far too much weight whether using free weights or machines. (3) Because of excessive weight they are not only at greater risk of injury, but they are also prevented from performing exercises through the full range of motion (AKA good form). (4) by not knowing or adhering to the principle of full range of motion, both muscle size and strength are significantly compromised. The exercise is either partially or wholly a waste of time and effort with very little results to show for it. Anyone who uses weight training as part of the means for losing body fat or increasing fitness, strength, or muscle mass should focus on learning the most effective and efficient way of doing so and with less risk of injury. A good place to start is doing a Google and Youtube search on "full range of motion" and that will lead you into the other issues I mention. 
Copy & paste this sharing link into your browser to see workout routines:
https://drive.google.com/drive/folders/1Hya-5fc_895vV9hoDMhv nQ4kMhOFGD2l?usp=sharing
It took me two years to work up to my current routines so I started out with very much lighter weight and did only 2 sets instead of 4. I also rested for two days between workouts to recover fully and now I can do every other day most of the time depending on how much activity (not weights) I do on my off day (Weekends throw me off some times as well). The number of reps are target reps. I always do the reps shown for the first set but sometimes I can only do less than that on the successive sets. I alternate Workout A with workout B so I can vary the exercise for a particular muscle (incline bench versus flat bench, hammer curls versus palms up curls, etc). I also vary the order that I do the exercises in to avoid always starting with full energy or less energy on the same exercise. Sometimes I do them in reverse order and sometimes in random order.
Because I have to focus on getting ample protein in my food regimen (I don't use anything other than my prescribed vitamins/minerals), I have to be concerned about taking in too many calories. I monitor my weight closely since measuring portions is not always the best indicator of my calorie intake. Since I get compulsive about my calorie intake I include other exercise on my off days and also on my DB workout days. I run, swim laps, and work the heavy bag for overall fitness and that has kept me at a resting heart rate of 56 BPM, low blood pressure, blood test values in the norm, and I don't have to take any prescribed medications. At that level of exercise I have to be concerned about over training, but so far that has not been a problem. I get ample sleep and I rest for more than a few days when my body says to take a break.
As with any exercise, no matter what it is, the main thing is to start out with no more than a comfortable level and work up slowly to the next level. Two years ago I started at 456 pounds and baby steps that took me to 220 pounds and a healthy, strong and fit state of being. I also learned a lot of important and valuable things along the way. Good luck!
