Here's my take on exercise while losing weight on Medifast. Some people can do it, some can't. You won't know which you are until you try. I could not exercise, even at a moderate intensity, while I was losing weight, because even with an extra shake, I wasn't getting enough calories. It would stop my weight loss, and I'd feel like crap afterward. Tired, sore, shaky, weak. But some people can, so I'd say try it. Following are my suggestions.
Eating: On days you exercise, add an extra shake and at least 2 more glasses of water. If you lift weights, have the shake within 30 minutes of finishing your workout. That's when your muscles are most receptive to getting the nutrients and building up, so you want to supply them with protein and carbs. No fat! If you're doing cardio, have a meal (any kind) no later than one hour before you start. Have a shake within 30 minutes of finishing and plan to eat another meal about 2 hours after that.
If you finish a workout and find yourself shaky or faint, drink water and have a shake immediately and rest. Next time, lower the intensity. If you ever feel faint or dizzy while working out, stop!
I've been doing some investigating, and it seems like the calorie counters on exercise equipment really overestimate how many calories you burn, but no one seems to know for sure.
Workouts - Cardio
I used to hate it, but it is good for your overall conditioning. Move at a brisk pace for 30 minutes 5 times a week. A brisk pace doesn't always mean out of breath and sweating. On this diet, you don't have a lot of energy to spare, so don't try to kill yourself. You just want to keep your metabolism active.
Alternately, buy a pedometer ($6) and try to get 10,000 steps in each day and don't worry about doing 'cardio'. Just walk around the house and keep track of your steps, and before long, you'll figure out ways to add another hundred here, a hundred there.
Workouts - Resistance
There's a ton of stuff you can do. Alex gave you same great ideas. She also hit on a sad truth. This diet, like all diets, eats away at your muscle. I'm so much weaker than I was before, it makes me sad. So don't go balls to the wall lifting because you can't eat enough to recover afterward. I'd aim for 3 sets of 6-10, and try to do compound movements. Those are exercises that move two or more joints. For example, bench press, overhead press, squats, deadlift, rows, pushups. And always do situps or crunches to build your core. You can PM me for tips about doing exercises correctly. When lifting, proper form is crucial both for muscle development and to prevent injury.
You can do 3 exercises, 3 times a week and get plenty of resistance work. Here's what I'm doing right now. It's quick and because they're all compound exercises, you work lots of muscles in just one exercise. Great for lazy people.
Monday: squat
bench press
bent over row
abs
Wed: squat
incline press (or overhead press)
deadlift
abs
Friday: squat
bench
bent over or upright rows
bicep curls
tricep extensions
For each exercise, do 3 sets of 6-10 using a weight that doesn't make you feel drained and out of breath by the last rep. If you can go to a gym, use a barbell and weights. If you're at home and can get dumbbells, you can do all these with dumbbells. Go to www dot exrx dot net and look through there for instructions and video on how to do the different lifts.
I picked up a set of dumbbells that are a bar and several 5 and 3 pound plates, so I can adjust the amount of weight on each dumbbell. Cost me about $40 at Sports Academy. It's a pain to change the plates all the time, but it's a lot cheaper than buying a bunch of dumbbells, and it takes up less space.
If you can afford it, I'd recommend a balance ball. They're great for doing situps and all kinds of exercises. I love doing bench presses on them because they work all my stabilizer muscles in the core too.
Finally, yoga is really really good for strength, balance and flexability. You could do that instead of weight lifting.
If you have no specific exercise equipment at home, you can do dips with a kitchen chair. Put your palms on the front edge, scoot your butt off the chair and lower your butt by bending your elbows. You'll feel it in your triceps. Do pushups. Oh, one-legged squats and lunges are fantastic for your legs and balance. Go to the site I mentioned above. I hate jump rope, but jumping jacks are fun.
Oh, here's an idea. Search for "The Hacker's Diet" and look at his exercise plan. It's set up for somebody to do at home with no equipment.
Finally, just look for opportunities. I'd put a bag of mulch over my shoulder and run to where I needed to put it, instead of walking there. If you've got a big rock in your yard, pick it up and put it down 10 times. Pick up a bag of cement or sand. Always make sure you use good lifting technique, ie, lift with your knees and make sure your back is straight.
I will say I disagree with Alex on the crunches. I think it's essential to work your core, and crunches are a great way to do it. There's a bunch of ways to do them. On a balance ball; lie on the floor with hands under your butt and lift your legs 12 inches off the floor, lower to 6 inches, repeat 20 times; sit on your butt with your legs up at 45 degrees and your upper body at 45 degrees, so your hips make a right angle, squeeze your abs to bring your legs in and release, repeat 20 times.
Flexibility
Stretch at the end of your workout, not before. Before your workout, do a light version of whatever your plan to do. If you're going to walk or jog, start out slowly for a few minutes. If you're going to lift, do a set or two that's super light, just to warm up the muscles and joints.
Sports
Find a sport you like and join up. That's a fantastic way to exercise, no matter what it is.