Although no one single food will provide miraculous weight-loss results on its own, eating a little more of certain foods, such as green apples, may help increase the amount of weight a person loses. This doesn't mean that you should eat only green apples -- or mainly green apples -- but when consumed in moderation, eating green apples can play a role in a healthy weight-loss diet.
Apples and Weight Loss
In general, apples, may help with weight loss. A study published in the journal Nutrition in March 2003 found that people who ate three apples or three pears a day as part of a reduced-calorie diet lost more weight than people who followed a similar diet, but who ate oat cookies instead of fruit. For weight loss to occur, apples need to replace higher-calorie foods. Simply adding apples to your diet without taking anything away won't increase weight loss.
Fiber's Effects on Weight Loss
Foods high in fiber may help people limit their risk for obesity in three ways, according to a review article published in Nutrition Bulletin in March 2007. First, these foods require more chewing -- which increases the amount of saliva that mixes with the food -- making the food bulkier and more filling. Second, fiber can result in a better absorption balance because eating high-fiber foods means that you will absorb slightly fewer calories than eating lower fiber foods. Finally, although fiber takes up space, it doesn't provide much in the way of calories, so high-fiber foods tend to have fewer calories. Apples are a relatively high-fiber food, as each medium Granny Smith apple with skin provides nearly 5 grams of fiber, out of the total recommended daily intake of 25 grams of fiber per day.
Energy Density and Apples
Diets that are lower in energy density -- or calories per gram of food -- can help people manage their weight, according to a review article published in the Journal of the Academy of Nutrition and Dietetics in May 2012. Foods lower in energy density help with weight loss because you can eat more of these foods and still consume fewer calories -- which helps people feel fuller -- even on a reduced-calorie diet. Apples have a very low energy density, making them a good weight-loss food.
Apple Polyphenols and Body Fat
Preliminary research shows that certain types of polyphenols found in apples may help increase weight loss. Polyphenols are beneficial plant chemicals that act as antioxidants, and they help limit cell damage in the body from substances called free radicals. A study published in Experimental Animals in 2006 found that these apple polyphenols helped limit body fat in rats. Further research is necessary to verify that this effect also occurs in people.
Green Versus Red Apples
Although all apple varieties have similar nutritional value -- when it comes to limiting the risks for obesity -- it seems that green Granny Smith apples have a small advantage over red or yellow apples such as the Gala or Fuji apples or the Golden or Red Delicious apple varieties. Granny Smith apples tend to have the highest number of certain types of polyphenols and fiber, which helps increase the beneficial bacteria in the gut of animal subjects, according to a study published in Food Chemistry in October 2014. Obese people tend to have lower levels of beneficial bacteria in their gut, which can increase their risk for metabolic disorders and inflammation.
The Form of the Apple Affects Fullness
The form in which you eat your apple will make a difference in how filling that apple is, and therefore how beneficial it is for weight loss purposes. Whole apples are more filling than applesauce, which is more filling than juice, according to a study published in Appetite in April 2009. To obtain the greatest benefit from your apple, eat it about 15 minutes before a meal. This preload may help you eat fewer calories during the meal, even if you consider the number of calories in the apple.
Other Nutritious Alternatives
Other fruits and vegetables may have weight-loss benefits similar to apples, so if you're not a fan of the apple, don't worry. A study published in the International Journal of Obesity in 2004 found that generally increasing fruit and vegetable intake limited the risk of weight gain and obesity. Non-starchy vegetables -- such as lettuce, tomatoes and broccoli -- are all low in energy density, as are most fruits, including berries and melon. Foods that have a high water or fiber content, such as most fruits and vegetables, tend to be lower in energy density, while those high in fat or sugar -- including many processed foods -- tend to be high in energy density.