Cutting out afternoon snacks and exercising may be the best way to keep your heart healthy in old age, research suggests.
Experts found combining crash diets with regular half-hour treadmill work-outs had little benefit other than weight loss.
Instead, chopping out 250 calories – the equivalent of three chocolate digestives or two packets of crisps – was the only one of three methods that appeared to boost heart health.
Academics at the Wake Forest School of Medicine in North Carolina admitted their discovery took them by surprise.
Researchers stuck 160 obese adults in their sixties and seventies into three different groups for 20 weeks.
A third of volunteers were asked to keep their regular diet but go on a treadmill four days a week for 30 minutes.
The others were also told to carry out the same amount of exercise but were instead asked to restrict their calorie intake.
Half were instructed to shave off 250 calories per day, while the others were told to cut out 600 calories.
The NHS says women should have 2,000 calories a day, while men should have 2,500.
The dieting volunteers received pre-made lunches and dinners but were given a list of breakfast items they could eat.
Results showed weight loss rates were similar between the calorie-restricted groups.
Those who cut the most calories lost 19.8lbs (9kg), on average.
For comparison, those in the moderate calorie-restricted group lost 17.6lbs (8kg), while those who only exercised lost just 3.7lbs (1.7kg).
But only those who cut out fewer calories saw significant improvements to their heart health, according to the researchers.
Experts monitored the stiffness of the aorta – the body's largest artery — among all the participants.
It gradually gets stiffer with age, making the heart work harder to contract and pump blood through the body, but obesity is also a risk factor.
Over time, stiffness can lead to an increased risk of heart failure and stroke.
People who ate 250 calories less per day had a 21 per cent increase in aortic distensibility – a measure of the artery's ability to expand and tighten to push blood around the body.
And they also saw an 8 per cent fall in pulse wave velocity – the speed blood travels through the aorta. A higher figure is associated with a stiffer aorta.
Dr Tina Brinkley, lead author, said the study is the first to assess the effects of aerobic exercise training with and without reducing calories on aortic stiffness.
She said: 'Our findings indicate these moderate lifestyle changes may help reduce aortic stiffness and improve overall vascular health in older adults.
'We were surprised to find that moderate caloric reduction and aerobic activity had a better effect on arteries than exercise with a more restrictive diet.'
Dr Brinley added: 'These relatively small changes should be manageable for people and more sustainable over the long term.'
WHAT SHOULD A BALANCED DIET LOOK LIKE?
Meals should be based on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally wholegrain, according to the NHS
• Eat at least 5 portions of a variety of fruit and vegetables every day. All fresh, frozen, dried and canned fruit and vegetables count
• Base meals on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally wholegrain
• 30 grams of fibre a day: This is the same as eating all of the following: 5 portions of fruit and vegetables, 2 whole-wheat cereal biscuits, 2 thick slices of wholemeal bread and large baked potato with the skin on
• Have some dairy or dairy alternatives (such as soya drinks) choosing lower fat and lower sugar options
• Eat some beans, pulses, fish, eggs, meat and other proteins (including 2 portions of fish every week, one of which should be oily)
• Choose unsaturated oils and spreads and consuming in small amounts
• Drink 6-8 cups/glasses of water a day
• Adults should have less than 6g of salt and 20g of saturated fat for women or 30g for men a day
Source: NHS Eatwell Guide