Exercising and maintaining a healthy lifestyle can be difficult at the best of times. But imagine doing it while not eating or drinking for most of the day. The Islamic month of Ramadan has started - with Muslims around the world abstaining from food or drink between dawn and sunset for 30 days.

Ramadan shifts according to the movement of the moon. This year it falls in the early summer, which means people in the UK will be fasting for around 18 hours a day.

Dr Ranj Singh, presenter of CBeebies show Get Well Soon, resident doctor for ITV's This Morning and former Strictly Come Dancing contestant suggests three key principles: eat and drink the right things during non-fasting hours, do light exercise and make sure you get enough sleep.

Dr Ranj Singh

Fasting for so many hours will have an impact on how much you can exercise. "Keep yourself fit and healthy, but don't overdo it as you could make yourself unwell," says Dr Ranj.

"So what type of activity is best if you're not to put too much strain on your body?"

Dr Ranj recommends brisk walking, gentle jogs and other light aerobic workouts, but stresses the importance of timing your exercises.

"Many people will find it easier to work out when they get up in the morning before dawn - that way they have had a chance to build their energy stores overnight. This is probably the best way since your muscles will need energy to be readily available."

However, Dr Ranj acknowledges that exercising so early in the morning may not be ideal for everyone. Many gyms are also now open 24 hours a day or you can exercise from the comfort of your home early morning.

Choosing to walk, instead of driving, to the mosque for evening prayers or taking the stairs rather than a lift are just a couple of ways in which you can introduce exercise into your daily routine.

With a window of around six hours a day when you can eat and drink, mostly overnight, it is important to think about what you consume in the pre-dawn meal and in your evening meal, to make sure you have enough energy throughout the day.

Dr Ranj advises that you avoid the temptation of too many sugary, oily or fried foods. "Firstly, make sure your diet is varied and has a good balance of all the major food groups - for example carbohydrate, protein and fat - including lots of fruit and vegetables," he says.

"Secondly, try to eat things that release energy slowly so you will feel less hungry between meals and it will keep you going, such as oats, whole-grains and high-fibre foods.

"Thirdly, pay attention to hydration and make sure you drink plenty. Drinking water is extremely important and you need to make sure you hydrate enough during non-fasting hours to keep yourself well. Levels of hydration will affect how much energy you have and your alertness during the day, which is why it is so important."

The month of Ramadan throws up many challenges, but 'everything in moderation' is the key concept when looking at what to eat and drink and how much to exercise, advises Dr Ranj.

He also sees the month as a chance for Muslims to make positive changes to their lifestyle.

"If you are going to fast, then use it as an opportunity to think about what you are eating and to make positive changes to your diet, and lifestyle.

Gym classes specifically tailored to its clientele of those fasting are getting them ready for the Holy Month"

Lauren Harrison, 24, who runs the class at the Fit Together Gym in Wigston, Leicestershire, said getting fit and healthy helped her clients get through.

A boxing coach in Stockton, Teesside, is running training sessions catered for those who still want to train during Ramadan.

Imran Naeem, from Natural Progression Boxing Academy, says the sessions are aimed at being done just before people break their fast.