All food provides some energy in the form of calories. However, some foods come packed with more energy than others. Nuts, including almonds, tend to have a relatively high number of calories per serving. That makes almonds a useful and healthy snack for delivering high energy in a small serving. Almonds also pack in other nutritional benefits such as high fiber content.
A calorie is a measure of the energy within a piece of food. Specifically, a single food calorie measures the energy required to increase the temperature of 1 kg of water by 1 degree Celsius. In terms of your body, this energy enables your muscles, organs and all other biological processes to function. The three main forms of fuel are carbohydrates, fats and, to a lesser extent, proteins.
A cup of whole almonds contains 822 calories, according to the USDA National Nutrient Database. Almost half of those calories come from fat -- the most calorie-dense of all food substances. Under 22 percent comes from carbohydrates, with over half of that total from fiber and around one-seventh from sugars. Protein makes up 21 percent of an almond's nutritional content. However, protein offers less immediate energy benefits than fats and carbohydrates.
The "Harvard Heart Letter" lists a variety of activities and the energy you expend when doing them for 30 minutes. At the low end, for example, a 155-lb. person can expect to burn 149 calories doing yoga. At the other end of the scale, running at 10 miles per hour for 30 minutes burns 614 calories in a 155-lb. person. That means that 1 cup of almonds provides easily enough energy in theory for most half-hour activities.
You most likely won't eat a whole cup of almonds in one sitting. However, as a mid-afternoon snack or a way to keep your energy levels up through the day, small handfuls of almonds work well. The high fiber content of almonds may produce a laxative effect in your body, increasing the speed of your bowel movements. You may want to avoid eating too many at one time for that reason.