It seems that calorie intake doesn’t matter as much as whether the food you are eating is actually healthy and good for you – confusingly, that’s even if some of the healthy foods like nuts are high in calories.
What the study found
The review by Harvard Medical School of three studies involving 120,000 people followed over 20 years found that those who ate more healthy foods lost weight, whereas those who ate unhealthy foods such as crisps, sugary drinks and meat gained weight.
When the researchers analysed their data in more detail, they found that people who ate an extra portion of yogurt a day, compared to the study groups, lost an average 0.82lb (0.37kg) every four years over a 20-year period. Those who ate an extra portion of nuts lost 0.57lb (0.26kg); those eating extra fruits, grains and vegetables lost 0.49lb, 0.7lb and 0.2lb respectively.
The researchers also found that those who consumed more unhealthy foods gained weight; for example, those who ate an extra portion of crisps every day gained 1.69lbs over four years, whereas those who drank sugary drinks gained 1lb, those who ate more unprocessed meat gained 0.95lb and those who ate more processed meat gained 0.93lb.
The team stressed that this didn’t mean that eating unlimited portions of healthy foods could lead to weight loss – just that people who ate them tended to eat less calorie-dense foods like crisps, meat and sugary drinks. The healthier foods were digested more slowly and had higher fibre content, making those who ate them feel fuller for longer. Put simply, they were full up with the healthier foods to eat too much calorie and fat-laden junk.
Should we all eat more nuts?
Dr Sarah Schenker says many people are wary of eating nuts because of their high fat and calorie content but the Harvard study is not the first to show that nuts are not associated with weight gain.
“This is largely due to the fact that eating only a relatively small quantity can make you feel full and that the body only absorbs about half the available calories,” says Sarah; “comparison of weight loss plans, where nuts are allowed or banned, show more people stick to the diet plan and achieve greater weight loss when nuts are permitted.”
“Nuts are rich in vitamins, minerals, essential fats and healthy oils,” adds Dr Sarah; “like fruit, they also contain substances associated with health benefits, such as reducing the risk of heart disease, which has prompted recommendations to increase their consumption.”
Walnuts, Brazil nuts and almonds, for instance, have all been shown to lower cholesterol.
What about fruit?
“Many popular diet plans do not allow fruit as it is thought to provide too much additional energy,” explains Sarah; “I would argue that including a variety of fruits in the diet is important for health because they’re a good source of vitamins and minerals, including folate, vitamin C and potassium.”
Different fruits also contain an array of substances that can help reduce the risk of heart disease, stroke and some cancers.
They are also an excellent source of dietary fibre, which helps maintain a healthy gut, preventing constipation and other digestion problems. A diet high in fibre can also reduce your risk of bowel cancer.
What’s the bottom line?
Basically, fruit, nuts, yoghurt, whole grains and vegetables make you feel full for longer, give you important nutrients and make it less likely that you will eat high-calorie junk foods.
Sarah says: “The bottom line is that fruit and nuts should be included in your diet in moderation – they taste great, are full of good quality nutrients and reduce the risk of disease without compromising weight loss or maintenance.
“But this doesn’t mean you can eat unlimited amounts of them – consuming too many calories overall will still lead to weight gain. Weight loss is generally best achieved by eating more healthily and being more active.”
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