Ask the doctor: I’m 50 and I want to drop a dress size — is intermittent fasting a healthy option?

Dr Grant replies: Firstly, it’s great that you are motivated to change your body and get healthier. You are correct to target your body fat and aim to fit into a smaller dress size rather than looking at your weight. Secondly, you are also right in saying intermittent fasting is a good way to lose weight and starting with the 16 hours of fasting and only 8 hours window to eat is quite easy to do.

Thirdly, you should exercise first thing in the morning as you can simply extend your natural overnight fast by just a few more hours. You want to be in a ketosis (fasting) state when you perform cardiovascular exercise and/or weight resistance training. Take plenty of water and maybe a tea/coffee but no milk or sugar. I also suggest you do weight-resistance training for only 15-20 minutes, three days per week and focus on the buttocks and quadriceps, the largest group of muscles.

Fourthly, you must calorie-restrict throughout the whole day to lose weight. Focus on getting 20-30g of protein in every meal but don’t forget the fibre. Eat two pieces of fruit with the skin or a portion of berries which are great low-sugar fruits. Lunch should be salad (you can never eat too much), no soup (as this won’t fill you for long) and protein (egg, tuna, chicken). Skip the carbohydrates such as bread, and pasta at lunch and only eat small portions at other meals. At dinner, aim for half a plate of vegetables with some protein and wholewheat/grain carbohydrate.

Fat-burning cardiovascular exercise is generally zone 1 (brisk walking, cycling or gentle jogging) when your heart rate is 50-60pc maximum for 30-40 minutes. You don’t need to do cardiovascular exercise every day. Your body will thank you for a few rest days every week. Your diet (what you eat and when you eat) is the most important driver of change in your body shape.

Lastly, there are a few endocrine disorders than can make weight loss very difficult. You should get a routine set of blood tests with your GP to assess your thyroid function, 9am cortisol hormone level, follicle stimulating hormone (FSH) and luteinizing hormone (LH), serum testosterone, oestrogen and sex hormone binding globulin (SHBG) levels. Hypothyroidism can make it very difficult to lose weight, but this is easily corrected by taking daily medication.

The cortisol blood test is to assess your adrenal gland function, as Cushing’s syndrome can sometimes be the underlying cause for difficulty in shifting the stubborn fat cells. FSH, LH and oestrogen can help determine if you are perimenopausal. The last few blood tests can assess for poly cystic ovarian syndrome (PCOS) as it is well known that this condition leads to increased body mass index. ​

Remember everything that crosses your lips for the next 10-12 weeks is part of your daily calorie count. Ensure you are sleeping well as this is the foundation of your health and try to reduce stress.

​Dr Jennifer Grant is a GP with Beacon HealthCheck