Training for Thryoid and Back/Knee Chronic conditions.

Can he get a referral from his doctor for physical therapy? Those folks can give him exercises to reduce the diagnosed problems, train him how to move differently in everyday life activities to reduce further strain, and suggest regular forms of exercise that will be most achievable given his specific physical challenges.

Other things that have helped me with back problems: Osteopathic manipulation regularly, massage from someone qualified at massage therapy (not just relaxation massage). Also, the fitter I get, the fewer back troubles I experience (not true for all, though).

What to do about the knees depends on exactly what the problem is. Both my rowing double partner (age 70 BTW) and I (61) have knee troubles (not caused by rowing ), an we have the same orthopedic specialist, but our treatments have been completely different (from doc & PT) because the underlying problems are different (she has kneecap arthritis, I have a torn meniscus/osteoarthritis in the joint). Icing after exercise (whether it hurts or not at the time) seems to help both of us. Weight loss dramatically improved my knee pain/discomfort, to the point of being mild & occasional vs. nearly constant and sometimes impairingly severe.

Exercise works just fine for me to burn extra calories, get fitter, etc., just as it does for anyone else, despite being hypothyroid. With careful logging, weight loss via calorie counting works fine, too. Some people report low carb being helpful for them while hypothyroid & losing weight, but I haven't found it necessary. Really, I haven't found that being hypothyroid makes any difference, once it's well controlled with meds.

Inactivity is, IMO, a big curse, especially as we age. Activity doesn't have to be big fancy exercise - just get up and move instead of sitting: Garden, do carpentry, walk, dance, anything. More intense exercise (cardiovascular & strength, and IMO flexibility as well) is really great for us, too, but just getting away from constant sitting is huge.

One diet note: There's some research suggesting it's even more important as we age to get extra protein, and to include a fair portion with each meal.

Reformer pilates is a great way to go especially for chronic pain sufferers. It's basically isometric exercises that consider proper body mechanics and mobility. I injured my back in 2015 when I started my weight loss journey. I was unable to do any exercise other than PT. Once I got more mobile, I started doing reformer pilates and it's made a huge difference for me. I also swim 1-2x per week and it helps my back related issues a lot.

Swimming or water aerobics is good as it can relieve back, hip and knees from body weight stress while building muscle and cardio vascular health.

I turned to yoga about 18 months ago for my back and it has helped more than I can say.

First of all this is awesome news that your success is inspiring others.

People tend to get mired into doing what they previously did and it is one of the most challenging parts of this - to break a habit. Our minds are wired towards habitual behavior, so every "bad" habit needs to be replaced with a "good" habit. What did your Dad to previously to stay in shape and what activity can he replace this with?

I look at all of this like a detective - writing down potential root causes and assuming all are true until proven otherwise. Do the same and write all varibles down, then investigate each one until you are left with a root cause:

1. Caloric intake - is he logging everything accurately? (noting the inherent 20% degree of error in calorie labels)
2. Caloric output - is he logging activity accurately? Thyroid does not impact your calorie burn at all.
3. Thyroid - this impacts Resting Energy Expenditure (REE) by ~5% from clinical observation. That equates to 80 kcals/day out of a 1600 kcal/day budget. Do not overestimate the impact thyroid has on weight management.
4. Thyroid panel results - TSH (0.2-2.0), fT3, fT4, rT3.

List anything else you can think of and don't stop and one why. Once you find an answer ask why again and again until you really get to the root cause - otherwise you're only treating a symptom.

Simply being overweight will complicate hormonal balance and makes it nearly impossible to function normally, so in any case the best course of action is safe, moderate diet and exercise achieving a calorie deficit.

As far as advice I'm a big fan of words of affirmation. Drive it home how proud you are that he's doing something and offer up tips. Everyone will take a different form of motivation, so try multiple strategies.

As for my story:
I was coming up for re-enlistment in the US Navy and a physician found a small lump in my throat while inspecting some scar tissue. After aspiration this was found to be cancerous, so I had a total thyroidectomy. This eliminated my front line career and I left, serving as a contractor and shifting to a career in academia as a microbiologist. I stopped working out and put on ~70 lbs over 14 years. My wife had used MFP to get back in shape after having our three kids, so I tried this out. I lost ~60 lbs in the first year just following the program and diligently documenting everything I ate. I gradually increased my workouts and nearly competing at the same level I did years ago.

Hope this helps.