I am 67 and have had a quad­ruple heart bypass and valve replace­ment. For the past four months I have been going to the gym two or three times a week and although I feel fit­ter, I can­not lose weight (I am 16^st). I got rid of my car and do much more walk­ing now, but still can­not shift this weight. Can you advise me?

Your frus­tra­tion at not being able to shed weight is under­stand­able. I think you may be being a bit hard on your­self, though. Even if you were unaware of it, you were prob­ably los­ing fit­ness, gain­ing weight and redu­cing your activ­ity levels for a year or two – pos­sibly much longer — before the moment of truth that led to your heart oper­a­tions. That slow decline can­not be turned around overnight.

Then there’s the effects of the oper­a­tions. Major heart sur­gery is, quite simply, exhaust­ing. The anaes­thetic alone can leave you drained of energy for months – more so if you are over­weight. Plus, your body is try­ing to knit back together all the wounds, and get used to the vari­ous drugs you’ll now be on.

These days the NHS has a good sup­port sys­tem for car­diac patients after sur­gery, with a strong and pos­it­ive emphasis on get­ting up, get­ting mov­ing and get­ting into good habits as soon as pos­sible. With all this encour­age­ment it is easy to for­get that you are almost cer­tainly start­ing out from a very low level of fit­ness and activ­ity, and your body can only rebuild slowly.

To lose weight you need to be act­ive enough every day to burn about 500 cal­or­ies more than you eat. If your fit­ness level doesn’t yet allow you to do that much activ­ity, you will not lose the weight, even though you are still doing essen­tial work improv­ing your fit­ness and rebuild­ing your body.

Your gym ses­sions and walk­ing are all excel­lent activ­it­ies. Make sure your pro­gramme includes weight train­ing as well as cardio-​vascular work (more muscle burns a lot more cal­or­ies). Make sure the gym staff update your pro­gramme every six weeks to keep push­ing you on.

As your energy levels increase, add in some activ­ity on the non-​gym days: swim, bor­row a dog for long walks, jog gently round the park, sign up for cycle rides, line dan­cing, tea dan­cing or dry stone-​walling. It really doesn’t mat­ter so much what you are doing as the fact that you are keep­ing on the move every day, gradu­ally step­ping up your over­all amount of activ­ity. But always listen to your body and expect this pro­cess to build over many months, rather than weeks.

Finally, check your eat­ing habits. Even if you are fol­low­ing all the healthy eat­ing guidelines, it’s very com­mon to allow your­self “rewards” once you get into a reg­u­lar exer­cise routine. If you can identify a single item (eg daily sweet or bis­cuit snack, sugar in tea, glass of wine) that you could elim­in­ate, it might tip the cal­or­ific bal­ance in your favour. Be patient and con­sist­ent, and you will shed the weight.