My 2 cents worth:
1. Symptoms such as tiredness, low energy etc can be caused by many illnesses. From Diabetes to infections. Do not assume it is low T. See your Dr and talk to him openly about your symptoms. The Doctor should come up with a list of differential diagnoses and test accordingly. Do not just test for T.
2. Losing weight and building muscle can absolutely increase T production (unless the testes have been irreparably damage by infection, radiation, chemotherapy etc).
3. For weight loss, caloric restriction and carbohydrate restriction is more important than exercise. The old adage "you cannot exercise your way out of a bad diet"
4. Strength training is very important for men older than 40 years. A study found that men who can do 40 push ups have a lower risk of heart disease. Note that strength training helps with weight loss but has to be combined with a caloric restricted diet.
Kudos to Boss for cycling 300km a week. Cycling is a great low impact aerobic exercise. At high wattage and hills also very good for building major muscle groups in the legs and lower back.
I'm really not here to plug my blog but I am very passionate about fighting obesity and am a member of the Singapore Association for the Study of Obesity. I wrote a piece of weight loss. It is long but hopefully useful:
https://drtanmenshealthblog.com/2021...eeping-it-off/