What is fat?
Dietary fat provides the body with essential fatty acids. Fat is broken down into fatty acids and glycerol in the digestive tract, and these fatty acids are then used for energy. Ensuring that you're eating enough dietary fat is vital for the absorption of the fat-soluble vitamins E, D, K, and A as well as cellular function, vision, hormone production, cardiovascular health, immune function, and glycemic control. Additionally, your brain is made up of 60% fat, so adequate intake helps support cognitive function and brain health.
Dietary fats are broken down into saturated, monounsaturated, polyunsaturated, and trans fats, and each category may have a unique impact on health outcomes. (33, 34)
| Type of Fat | Background | Main Dietary Sources |
| Saturated Fat (SFA) |
SFA intake is hotly debated because the research is inconclusive and/or shows conflicting results. It is important to consider the possibility that there may be genetic predispositions that determine our personal response to SFA. Being more sensitive to cholesterol or saturated fat intake may moderately increase cholesterol and increase the risk of heart disease. To understand your unique risks and responses to SFA, we recommend that you talk to your primary care physician about your unique risks and ask for an advanced lipid panel every year. (35, 36, 37, 38) |
Beef, lamb, pork, tallow.
Cured meats - sausage, bacon, salami.
Full-fat dairy - cream, milk, yogurt, cheese, butter, ghee, ice cream cream, butter, cheese, ice cream, cocoa butter.
Coconut, palm oil. |
| Monounsaturated Fat (MUFA) |
MUFAs have been shown to help fight against inflammation and may be linked to a reduction in chronic disease. In fact, avocados have been shown to improve post-meal blood glucose and insulin concentrations as well as decrease abdominal adiposity. (39, 40) |
Vegetable oils including olive oil, peanut oil.
Olives, almonds, hazelnuts, pecans, pumpkin seeds, sesame seeds, and avocado. |
|
Polyunsaturated Fat (PUFA) |
PUFAs include Omega-3 and Omega 6 fatty acids. Today's research shows that a high intake of omega-6 fatty acids compared to omega-3 fatty acids is pro-inflammatory. We know that inflammation is an underlying cause of many metabolic complications and that the ideal ratio for omega-3:omega-6 is 4:1. To help meet this ratio, aim for whole food sources of omega-3s while avoiding refined vegetable oils and trans fat. (41, 42, 43) |
Omega 6 fatty acids: Vegetable oils, also known as "seed oils" - sunflower, safflower, soy, sesame, corn, canola (rapeseed), rice bran.
Omega 3 fatty acids: SMASH fish - salmon, mackerel, anchovies, sardines, Herring.
Processed foods - chips, cereal, some frozen meals, sandwich bread,
Pecans, brazil nuts, pine nuts, almonds, cashews, walnuts.
Poultry.
Flaxseeds, chia seeds, avocado. |
| Trans Fat |
These fats are artificially produced and have been linked to an increased risk of cardiovascular disease. These fats should be eliminated from the diet or consumed as minimally as possible. (39) |
Margarine, some peanut butters, non dairy coffee creamers, canned frosting,
Baked goods made with vegetable oil, shortening/margarine - doughnuts, cakes, pies, biscuits, cookies. |
Fat and glucose
Fat has a minimal effect on glucose. Because of this, it can be easy to view fat as a "free food." However, fat is our slowest digesting macronutrient and can take the longest to fully process. While this has many positive benefits including increased feelings of fullness and a smaller glucose peak, too much fat can lead to delayed glucose responses that take longer to return to baseline. Some fat in our meals is helpful for this reason, such as a balanced pairing of nuts with fruit, but too much causes our body to continue to 11process11 the food for a long time, which can result in a longer insulin response. When it comes to fat, portion size, and meal composition is important to consider. (44, 45)
The debate rages on whether saturated fat (SF) intake contributes to poor metabolic outcomes such as insulin resistance and diabetes. When thinking through the lens of promoting insulin sensitivity, one study found that eating a high-saturated fat diet had a negative impact on insulin sensitivity in healthy individuals. A longer study with higher saturated fat intake found that after three months, insulin sensitivity decreased by 12.5%. In some studies, reducing saturated fat intake and leaning on more monounsaturated fat sources have been linked to improvements in insulin sensitivity in some individuals. It's important to note that these studies included an intake of 17-25% calories from saturated fat, which is much higher than typical institutions recommend.
However, there's no one-size-fits-all approach to dietary fats and saturated fats specifically. It's important to consider your overall intake, and genetic and lifestyle variants to understand what's right for you.
Fat and Weight Loss
There have been interesting studies demonstrating that both low-fat and low-carb diets have beneficial effects on metabolic risk factors and weight loss. One meta-analysis from 2022 looked at 33 studies involving a total of 3,939 participants. At 24 months, there were no significant differences in weight loss success and improvement of metabolic risk factors between the two groups. It should be noted that those following low-carb diets saw greater reductions in triglycerides and increases in HDL up to the 24-month mark. This suggests that both a low-fat and a low-carb diet can be effective for weight management, but finding a diet that you can stick to may be the most important factor for long-term success. (49, 50)
As discussed previously, it's important to remember that fat has more calories per gram than carbohydrates or protein. This means that a high fat intake can take up a larger portion of your overall calorie intake goals. When planning meals, it can be helpful to aim for a balanced intake of fats, protein, and carbohydrates.
Quality matters
While fat has been demonized by health institutions for decades, fat is not solely to blame for weight gain and is a critical component of a healthy diet. That said, not all fats are created equal, and being strategic about the types of fats you choose is important. (51) The lists below are general guidelines that can work well for most individuals.
Healthy fats to include:
- Olives, extra virgin olive oil
- Avocado
- Most nuts and seeds (almonds, pecans, walnuts, pistachios, brazil nuts, hazelnuts, chia, flax, and pumpkin)
- SMASH fish (Salmon, Mackerel, Anchovies Sardines, and Herring)
- Fat from pasture-raised, cage-free eggs
- When choosing animal products like beef, pork, eggs, and dairy, opt for pasture-raised/grass-fed products, if you're able.
Fat sources to limit:
- Processed meats like sausage, bacon, and pepperoni (tend to be high in sodium and contain additives and nitrates)
- Trans fats (hydrogenated oils)
- Polyunsaturated vegetable oils, "seed oils"
- Fats from processed foods that are also high in simple carbohydrates, such as pizza, fried foods, macaroni, cheese, etc.
As with other macronutrient groups, whole food sources are always the best options to include in a well balanced diet.