A large study spanning over 20 years found that people who increased their olive oil consumption gained less weight over time compared to those who used other fats in their diet. The findings challenge long-held beliefs about dietary fats and weight gain, suggesting that the type of fat we consume may matter more than how much fat we eat overall.
What the Study Found
Researchers meticulously tracked more than 121,000 men and women across the United States for two decades, checking in on their diets and weight every four years. The study, published in The American Journal of Clinical Nutrition, analyzed data from three well-known health studies: the Nurses' Health Study, Nurses' Health Study II, and the Health Professional's Follow-up Study.
Here's what they discovered:
- People who added just half a tablespoon (about one teaspoon) of olive oil to their daily diet gained slightly less weight over each four-year period
- In contrast, people who increased their consumption of butter, margarine, or other vegetable oils tended to gain more weight
- The biggest difference was seen when comparing olive oil to butter - replacing a half tablespoon of butter with olive oil was linked to about one pound less weight gain over four years
- Even substituting olive oil for carbohydrates like white bread or pasta showed small benefits for weight management
The Weight Management Challenge
Weight gain is common as people age. In this study, participants gained an average of 2 to 4 pounds during each four-year period, with younger women gaining the most weight. This gradual weight creep can lead to obesity and related health problems over time.
This study is particularly valuable because it focuses on real-world eating patterns over many years rather than short-term diets or laboratory conditions. The researchers repeatedly measured both diet and weight over two decades, allowing them to see how changes in specific foods related to changes in weight within the same person over time.
Not All Fats Are Created Equal
The findings challenge the common belief that all high-fat foods lead to weight gain. While olive oil contains just as many calories as other oils and fats (about 120 calories per tablespoon), something about it affects the body differently.
Scientists believe several factors might explain why olive oil doesn't promote weight gain like other fats:
- It's rich in healthy monounsaturated fats, particularly oleic acid, which may help regulate appetite and metabolism
- It contains unique plant compounds called polyphenols that have anti-inflammatory properties
- Olive oil may increase feelings of fullness compared to other fats
- It might subtly boost calorie burning through a process called thermogenesis
- People who use olive oil often consume it with vegetables, which might lead to healthier eating overall
Who Benefits Most?
Interestingly, the research found that olive oil's benefits for weight management were strongest among certain groups:
- People under the age of 50
- Those who were already overweight or had obesity
- People with Southern European ancestry (though the benefits were seen across all ancestry groups)
Simple Swaps That Might Help
Based on the study results, making small changes in your cooking habits could potentially help with weight management over time:
- Use olive oil instead of butter on bread or toast
- Sauté vegetables in olive oil rather than margarine or vegetable oil
- Make salad dressings with olive oil instead of creamy, butter-based options
- Try olive oil in baking recipes that call for butter or vegetable oil
- Drizzle olive oil over cooked vegetables instead of adding butter
- Use olive oil when roasting potatoes or other vegetables
- Try dipping bread in olive oil instead of spreading it with butter
Mediterranean Diet Connection
The findings align with what researchers have observed about the Mediterranean diet, which features olive oil as its primary fat source. People from Mediterranean countries like Greece, Italy, and Spain traditionally have lower rates of obesity despite consuming relatively high amounts of fat through olive oil.
"Our study findings contribute additional evidence suggesting that even in populations outside the Mediterranean region, olive oil consumption may serve as a favorable source of dietary fat without contributing to weight gain over time," the researchers noted.
The PREDIMED trial, a large study conducted in Spain, previously found that people following a Mediterranean diet supplemented with extra virgin olive oil did not gain weight over five years despite not restricting calories. Some participants even showed reductions in abdominal fat, which is particularly harmful to health.
Quality Matters
Not all olive oils are created equal. Extra virgin olive oil, which is less processed than regular olive oil, contains more of the beneficial plant compounds that might contribute to health benefits.
While the current study didn't distinguish between different types of olive oil, previous research suggests that extra virgin olive oil may offer the most health advantages. This type of oil comes from the first pressing of olives and has more of the natural compounds that give olive oil its distinctive flavor and potential health benefits.
The Fine Print
The researchers note their study has some limitations that are worth keeping in mind:
- Participants self-reported their diet and weight, which isn't always perfectly accurate
- Most people in the study were health professionals of European ancestry, so the findings might not apply equally to everyone
- The study shows a correlation between olive oil and less weight gain but doesn't prove that olive oil directly causes weight loss
- The actual differences in weight were modest—less than half a pound over four years for each half-tablespoon of olive oil consumed daily
Beyond Weight: Other Health Benefits
While this study focused on weight, previous research has found numerous other benefits associated with olive oil consumption:
- Reduced risk of heart disease and stroke
- Lower risk of type 2 diabetes
- Decreased inflammation in the body
- Improved cholesterol levels
- Lower blood pressure
- Reduced risk of certain cancers
- Better cognitive function as we age
Putting It All Together
So what does this all mean for your dinner plate? Replacing less healthy fats with olive oil could be a simple dietary strategy that offers multiple health benefits, including modest help with weight management.
Rather than focusing on cutting fat entirely, which often leads to increased consumption of refined carbohydrates, consider upgrading the quality of fats in your diet. Olive oil is one of the healthiest choices available.
"These findings suggest that substituting olive oil for other sources of fats may help prevent weight gain," the researchers concluded. "This evidence highlights the potential importance of dietary fat quality and sources for long-term weight control as well as the risk of cardiometabolic diseases."
While olive oil isn't a miracle food that will melt away pounds on its own, this long-term study suggests that choosing it over other fats might be a simple dietary change that could help keep your weight stable over time—while simultaneously supporting your overall health.
