Each type of fat has a different impact on weight.
The calories from any type of oil will contribute to weight gain if you consume too much. Some oils are more likely to pack on pounds, however, while others may help you lose weight when they're consumed as part of a balanced diet. Just as the ratio of good to bad fats in your diet affects your heart health, the different types of fats in vegetable oil influence your weight.
Calories in Oil
If you consider calories only, all oils are equal. Some oils weigh a little more than others, so you may see a small difference in calories per serving on nutrition labels of different brands. But you can figure on getting 120 calories in 1 tablespoon of all types of oils. Oils don't contain protein or carbohydrates, so all of the calories come from fats. You'll get about 13 grams of total fat in each tablespoon of oil. About 20 to 35 percent of your total daily calories should come from fats, according to the Institute of Medicine.
Type of Fat Matters
Choosing the oil that is most likely to cause weight gain -- or help you lose it -- comes down to identifying the amount of each type of fat in the oil. Consuming saturated fat from any source increases your risk for obesity, while unsaturated fats are not associated with weight gain, according to Field et al. in the April 2007 issue of the scientific journal "Obesity." Monounsaturated fats are more likely to help you lose weight than polyunsaturated fats, report Krishnan and Cooper in the December 2013 issue of the "European Journal of Nutrition." In a study in the May 2013 issue of "Obesity Research and Clinical Practice," Munro and Garg concluded that omega-3 polyunsaturated fats do not seem to promote weight loss.
Fat Profile of Oils
Vegetable oils, which are liquid at room temperature, are low in saturated fat but contain varying proportions of monounsaturated and polyunsaturated fats. You'll get 1 to 2 grams of saturated fat per tablespoon of oil no matter which type you prefer to use. Sunflower, flaxseed, grapeseed and safflower oils have the most polyunsaturated fat, with 9 to 10 grams in a 1-tablespoon serving. The two best sources of monounsaturated fat are canola and olive oil. Canola oil has 8.9 grams of monounsaturated per tablespoon, while olive oil provides 9.9 grams in the same serving. Peanut oil is the next best source, with 6 grams of monounsaturated fat in 1 tablespoon.
One Oil to Avoid
Research indicates that palm oil, which contains 6.7 grams of saturated fat per tablespoon, may cause weight gain. In one study, researchers prepared muffins using either palm oil or sunflower oil. Participants who consumed muffins with palm oil gained two times more visceral fat than those who ate muffins containing sunflower oil, according to the online edition of вЂњDiabetesвЂќ in February 2014. An earlier study published by de Wit, Derrien et al. in the September 2012 issue of the вЂњAmerican Journal of PhysiologyвЂќ reported that lab mice fed palm oil gained more weight than mice that ate olive oil and safflower oil.