Almonds recommended as best the go-to snack for people watching their weight 

They've traditionally been cut from diets because of fears their high calorie and fat content will make people fat. 

But nutritionists now say you don't need to have a guilty conscience if you tuck into nuts - especially almonds - this Christmas.

Experts at King's College London claim that while nuts do pack a lot of energy, the calories are not absorbed by the body.

Tests have shown as much as 20 per cent of fat in nuts, and a quarter of the calories, do not get absorbed, the Daily Mail reports.

Dr Sarah Berry, of King's department of nutritional sciences, said: 'Our research shows how important it is to look past food labels on some foods.

“What is displayed in terms of fat and calorie content may not accurately reflect what actually happens once consumed.

”'Nuts are a great example of this and it is crucial we move away from the long-held belief that they are full of calories and make us gain weight.

“Indeed, we have shown these to be a great snack choice, holding numerous benefits for our gut and cardiovascular health.”

In the recent KCL study, scientists compared fat absorption after eating a muffin made with trendy almond flour with one containing small nut pieces. 

They found fat remains trapped within an almond's structure throughout digestion and does not get absorbed.

When the nut is ground into a flour, however, its structure is broken down, which makes its fat more accessible and readily absorbed.  

The researchers ground almonds in a coffee grinder into both small pieces and a flour consistency. Ground
almonds are often added to gluten-free cakes as a flour replacement or to make baked goods 'healthier'.

Some 85g of either the almond pieces or the flour was then added to a muffin recipe, with the remaining ingredients being the same between the two types of muffin.  

Once the muffins had been chewed, but not swallowed, by some volunteers, they were added to a gastric model that simulates human digestion. 

This allowed the researchers to test the samples at different times throughout the digestion process. 

Results showed 57 per cent of the fat within the small almond pieces was digested compared to 97 per cent in the almond flour. 

In a second part of the experiment, the researchers recruited volunteers who had their lower bowels removed and stomas fitted following cancer, ulcerative colitis or Crohn's disease.

The stomas allowed the scientists to take fluid from the participants' guts to measure its fat and sugar levels. 

Results showed that eating the muffins with small almond pieces caused 56.5 per cent of the fat to be digested, compared to 96.5 per cent of the fat in the nut flour.