my friend alice says that part of my problem when walking after eating when it is warm is from dehydration which occurs with older people. she says she gets dizzy.
from mayo clinic
"Older adults. As you age, your body's fluid reserve becomes smaller, your ability to conserve water is reduced and your thirst sense becomes less acute. These problems are compounded by chronic illnesses such as diabetes and dementia, and by the use of certain medications. Older adults also may have mobility problems that limit their ability to obtain water for themselves."