For people aiming to get healthy, a change in diet in conjunction with exercise, is much more beneficial than starting with one of these and trying to incorporate the other later.

In fact, according to US scientists, tackling diet first, which many people attempt, may interfere with the establishment of a proper exercise routine.

While many studies have been carried out on diet and exercise separately, few have looked at the effect of doing these two things together. Scientists from Stanford University decided to look into this further.

They split 200 people into four groups. All of the people were aged 45 or older and had poor diets to begin with. Each group received a different type of coaching over the telephone, aimed at supporting them to make changes.

The first group made changes to both their diet and exercise regimes at the same time. The second group made changes to their diet first and did not attempt to change their exercise regime until a few months later.

The third group changed their exercise regime first, followed by their diet a few months later. The fourth group made no changes at all, but were taught techniques to manage stress.

All four groups were monitored for a year.

The study found that those who changed both diet and exercise at the same time were most likely to reach 150 minutes of exercise per week - that is equivalent to 30 minutes a day, five days a week. They were also the most likely to consume at least the recommended five servings of fruit and vegetables per day and get no more than 10% of their daily calories from saturated fats.

The group who began with exercise changes, followed by diet changes at a later date, also did a good job of achieving both diet and exercise goals. However, they did not do as well as the first group.

The group who began with changes to their diet, succeeding in meeting these goals, but they did not meet their exercise goals when they tried to make changes in this area later.

The scientists suggested that this is because there are very different challenges involved with both of these changes.

"With dietary habits, you have no choice; you have to eat. You don't have to find extra time to eat because it's already in your schedule. So the focus is more on substituting the right kinds of food to eat," they explained.

However, people often do not have exercise built into their daily schedule and have to find the time to do this. This can be difficult if a person has a busy schedule. In fact, they noted that even the first group had problems meeting the exercise goals at first, but over the course of the year, they figured out how to overcome this.

The scientists concluded that it is most likely ‘particularly useful to start both (diet and exercise changes) at the same time'. However, if for some reason, you need to start with one, ‘consider starting with physical activity first'.

They noted that the participants in this study were not actively seeking to lose weight, simply to get healthy. However, they are going to carry out the same approach in people who are actively attempting to lose weight.

Details of these findings are published in the journal, Annals of Behavioral Medicine.