Scientists from the US Department of Agriculture (USDA) found that a 28g serving of almonds (about 23 almonds) contained 129 calories compared with 160 calories listed on labels.
"When an 84g serving of almonds was incorporated into the diet daily, the energy digestibility of the diet as a whole decreased by 5%,” noted the scientists.
“Therefore, for individuals with energy intakes between 2,000 and 3,000 kcal/day, incorporation of 84g almonds into the diet daily in exchange for highly digestible foods would result in a reduction of available energy of 100–150 kcal/day.”
They said: “With a weight-reduction diet, this deficit could result in more than a pound of weight loss per month."
The results follow previous research showing that the macronutrients in almonds, including fat, are only partially absorbed during digestion. This is attributed to the fibre content and/or the rigidity of almond cell walls, which encapsulate macronutrients and make them unavailable for absorption during digestion.
Consequently, traditional methods of calculating the energy value of almonds result in gross over estimations, since they do not account for the fact that macronutrient digestibility in almonds is not 100%.
Dr Geoff Livesey, registered public health nutritionist, said: “I find the research about new, corrected calculations for almonds to be encouraging.
“The Baer calorie study is an example of how a healthy, nutrient-dense food, like almonds, has 20% fewer calories than previously thought. I hope we see further research in the coming years to investigate more foods, in the context of a mixed diet, and their genuine caloric values.”
The US research team, lead by David Baer, recently conducted a similar study using pistachios. They found a 5% decrease in pistachios' calorie count compared with the 20% decrease in almonds.
The team expanded on the traditional Atwater calorie test, devised 100 years ago, using a specially designed diet and a more precise method of measurement. This allowed them to understand the calories provided by almonds when eaten as part of a mixed diet.
Livesey said: “I hope the research encourages people to choose nutrient-dense foods like almonds. Having accurate calorie information helps consumers make healthier food choices.”
A recent survey revealed that being overweight was the top health condition affecting respondents across western Europe. Accurate information about the energy value of foods is important to consumers, health professionals and food manufacturers, said Livesey.
Dr Karen Lapsley, chief scientific officer for the Almond Board of California, said: “This new information indicates we get fewer calories than we thought from a handful of almonds. It may help explain, at least in part, why research participants in a recent almond study did not gain weight when they added almonds to their daily routine.”