Some people believe that throwing away the knife and fork is sufficient to lose weight. That sounds to me like a good definition of a “Diet”. Whilst such an extreme approach does work temporarily, I don’t think that it is needed.
Paying more attention to what is being placed on the knife and fork will achieve exactly the same goal but in a far more successful and long lasting manner.
The same holds true for exercise. I think that aggressive running, cycling, swimming, or power walking is best left to athletes who have their regular routines. Going to the gym might be an enjoyable activity and it needs to be considered just that, no more than an enjoyable activity. It is not a long term weight management tool if it can’t be done long term.
Doing some gentle walking most days is plenty enough to lose some weight and keep it off. The key is to actually do it. It is more likely to be done if a decision is made about what is realistic and achievable on most days, in most weathers. The length of a walk is different for everyone. There will be some optimal distance, ranging from from a kilometer or so right down to some small number of painful, slow steps across the house on a walking frame.