How to Add Healthy Fat to Your Diet

What eating plans reduce metabolic disorders?

There is no eating plan that suits everyone. However, there are some good guidelines to follow regarding macronutrient content that promotes metabolic health.

By taking these guidelines into account, nutritional and medical professionals can craft dietary fat recommendations driven by nutritional science not guesswork. It is great for individuals who want to take their health into their own hands too!

1) Metabolic diseases are fueled by excess food (energy)

MetS seems to be driven by a combination of a dietary energy surplus and a dietary carbohydrate intolerance (Hyde et al. 2019). One theory as to why this happens is the redox (reduction-oxidation) theory of MetS, obesity and T2D (Koac et al. 2021). Redox reactions refer to reduction, the gain of electrons, and oxidation, the loss of electrons. Redox reactions occur during oxidation of food energy, where the food derived electrons, carried by energy molecules, feed into the electron transport chain (ETC) within the mitochondria. Electrons are used to create an electrochemical gradient in the mitochondria which ultimately provides the energy potential to generate ATP.

What is the redox theory of MetS?

In the redox theory of MetS, continuous overeating overloads fat and glucose pathways causing glucotoxicity and lipotoxicity (sugar and fat toxicity). This whole system breakdown leads to an overproduction of the energy carrying molecules, nicotinamide adenine dinucleotide (NAD, NADH) and flavin adenine dinucleotide (FAD, FADH2). These molecules feed into the electron transport system. The excess energy influx stresses and eventually overloads a highly regulated system. This eventually leads to excess production of dangerous reactive species, mostly reactive oxygen and nitrogen species (ROS and RNS). In addition, feedback and accumulation of energy carrying molecules and radical metabolites can inactivate enzymes involved in the glycolytic pathway. This can lead to activation of alternative pathways of glucose metabolism which can deplete production of a vital internal antioxidant, glutathione (GSH). The end result is a storm of inflammation leading to MetS. For a highly detailed diagram and discussion of redox changes that can lead to MetS, see Korac et al. (2021).

There is no magic diet that will allow people to overeat consistently and remain metabolically healthy. Too many calories in any form, but especially sugar and fat, will promote metabolic disorders by promoting inflammation (Samocha-Bonet et al. 2012, Dali-Youcef et al 2012, Lecoultre et al. 2013, Silva Figueiredo et al. 2017, Choo et al. 2026). Caloric reduction or intermittent fasting, which uses calorie restrictions for one to several days a week, will improve metabolic health while reducing fat mass (Zubrzycki et al. 2018). 

J. E. Rogers, Jack Sprat could eat no fat book illustration c1869.

2) Persistently high insulin levels can cause metabolic disorders

There is evidence that persistent high insulin levels and dysfunctional insulin responses contribute to metabolic syndrome (Nolan et al. 2019, Ludwig et al. 2021). Dietary patterns that contribute to this, such as snacking continually throughout the day or consuming highly processed carbohydrates, will increase inflammation and accelerate the development of metabolic disorders (Hyde et al. 2019, Ludwig et al. 2021).

High insulin levels can result in burn out due to inflammation. Below a lone burnt tree stands after a fire.

Diets that encourage food breaks, such as intermittent fasting diets or eating within a specific window of time, are popularly recommended to improve glucose and lipid metabolism but more human studies are needed (Antoni et al. 2017, Pinto et al. 2019). Current studies show that both caloric restriction and intermittent caloric restriction are effective. Pinto et al. 2020 reported that five days of either an intermittent energy restriction (IER) or continuous energy restriction (CER) diet in men and women with central obesity (35-37 years) had fairly similar effects on markers of cardiometabolic health in individuals with central obesity. Both groups lost about the same amount of weight but fasting plasma glucose concentrations were only decreased after continuous energy restriction not after intermittent energy restriction.

Men and women (18-65 years) with metabolic syndrome showed similar changes in metabolic syndrome biomarkers with either an intermittent energy restriction or a continuous energy restriction diet. Both groups lost approximately 7% of their bodyweight and had similar reductions in total cholesterol, triglyceride, low-density lipoprotein (LDL), blood pressure, fasting glucose, and insulin. In both these diets, energy restriction combined with weight loss have a beneficial effect on markers of cardiometabolic health (Pinto et al. 2019).

3) A moderate to high fat diet can promote metabolic health even without weight loss

Any diet that causes weight loss will reduce some of the risk factors for metabolic disorders. However, since many people find weight loss or counting calories difficult, it is important to focus on diet recommendations that improve metabolic parameters even without accompanying weight loss. These include a moderate to high fat and/or protein diet with moderate carbohydrate intake. Diets that reduce carbohydrates while increasing protein and fat improve markers of MetS in people who are obese (Hyde et al. 2019, Willems et al. 2021).

Hyde et al. 2019 reported in a cross over study that a very low carbohydrate diet (74% fat, 20% protein, 6% carbohydrates) reversed MetS within 4 weeks independent of weight loss in the majority of their participants with obesity (average body fat 40%). The low carbohydrate diet enhanced fat oxidation while improved circulating lipoproteins and fatty acid composition (Hyde et al. 2019). Interestedly, since this diet emphasized natural foods, it utilized a high percentage of cheese.

In a cross over trial, women who were overweight or obese (body mass index >25) followed either a moderate carbohydrate diet 43-47% carbohydrate, 36-40% fat) or high carbohydrate diet (43-47% carbohydrate, 36-40% fat) for 6 weeks (Rajaie et al. 2013). After a 2 week wash out period, the women switched to the other diet. The high carbohydrate diet increased serum amyloid A (SAA), an inflammation marker, while decreasing levels of adiponectin, an adipokine that regulates glucose levels and FA oxidation. An increase in inflammation markers was not seen with the medium carbohydrate diet [276]. Low levels of adiponectin are not ideal. They are associated with NAFLD in Japanese men (Yatsuzuka et al. 2013).

Although extreme diets, such as very severe carbohydrate restriction, work in the short term most people will not tolerate them. Advising a more moderate macronutrient distribution will reduce MetS risk and/or symptoms while being more tolerable to patients. In general, fats should compose around 25-40% of the diet. People with metabolic disorders will benefit from replacing some carbohydrates with fats. Research on MetS diets suggests that replacing carbohydrates with fats of any kind will lower blood pressure, lower TG and increase HDL (Mensink et al. 2003, Rajaie et al. 2013, Clifton et al. 2019, Garr Barry 2021).

In particular, decreasing processed carbohydrates in diet will improve metabolic health. Fats are best consumed in whole food form. Good dietary sources of fat include tree nuts, avocadoes, full fat dairy, chocolate, seeds, olive oil, meats and fatty fish.

4) Fats to avoid or reduce

Avoid industrial TFA, fats in highly processed foods, highly refined or deodorized oils and reheated oils [291, 292, 293]. Industrial TFAs should not be consumed in any form. Stay away from any human made trans fats. Natural TFAs, such as those from dairy, are safe and overall seem beneficial. SFAs in highly processed foods or processed meats should be reduced or eliminated from the diet. SFA naturally occurring in foods have a mixed effect on health. More research is needed but it is looking like natural SFA are healthier than previously believed and do not contribute to cardiovascular disease [293].

Processed and hydrogenated fats can contain contaminates that affect health. Hydrogenated oils contain TFAs. Highly refined, bleached and/or deodorized oils have an adverse effect on health while the same virgin oils or fats do not. For example, older research showed highly refined coconut oil to be atherogenic and raise serum cholesterol in animals [294]. Recent research has shown that minimally processed virgin coconut oil does not raise serum cholesterol concentrations [295, 296]. Many older fat studies were done using highly refined vegetable oils which are not the same as using more modern minimally processed oils. Virgin oils are processed gently under low heat which retains nutrients and phytochemicals. Highly processed oils and fats are generated using high heat and/or chemical processes such as free fatty acid removal, bleaching and deodorizing. This can denature vitamins and antioxidants while adding carcinogenic contaminates such as triglyceride derivatives glycidyl and monochloropropandiol (MCPD) esters [297, 292]. Researchers cannot judge the health risks of high-quality fats from food by using studies that mainly looked at consumption of refined low quality dietary fats.

Do not over eat any fat. Consistently overeating a high fat diet (or a high carbohydrate diet) will contribute to metabolic disorder and inflammation (Samocha-Bonet et al. 2012, Dali-Youcef et al 2012, Lecoultre et al. 2013, Silva Figueiredo et al. 2017, Choo et al. 2026). 

5) Whole food diets are best

Fats should be added to the diet in whole foods. Whole foods contain fiber, nutrients and phytonutrients that can modulate inflammation [282].

Ultra-processed energy dense foods and excess added sugar are much more harmful than a whole food diet of any type [265]. Ultra-processed foods (UPF) are edible products formulated from food derived ingredients, that are made from a sequence of industrial processes. Ultra-processed foods include packaged snacks, soft drinks, packaged cookies, instant soups, prepackaged ready to eat/heat meals and more. The combination of processed carbohydrates, low fiber, added sugar and added fat in a processed food high caloric diet is especially harmful to metabolic health.

Ultra-processed diets are higher in poor quality SFA, carbohydrates and sugars; and lower in fiber, protein, vitamins (A, C, D, and E), zinc, potassium, phosphorus, magnesium, and calcium than healthier less processed diets [88]. Ultra-processed diets are also positively associated with MetS; people consuming a diet with over 70% ultra-processed foods had a 28% greater prevalence of MetS compared with people consuming a diet with less than 40% ultra-processed foods [91]. Currently 59% of the calories consumed in the USA are from ultra-processed foods [283].

Whole food diets are those that include vegetables, grains, fruits, nuts, oils, meats, dairy, fish, poultry and other food in as natural a state as possible. Consumption of a healthy diet pattern; i.e., whole foods with a high content of minerals, minerals, fiber, antioxidants, MUFA and omega-3 FAs, may reduce the risk of MetS [284, 285, 286, 287, 288]. An apple is a whole food. An apple pie is an occasional desert. A shelf stable ‘apple pie’ sold at a gas station is a processed product.

Whole foods take more energy to digest than highly processed food. Barr and Wright (2010) found that a processed cheese sandwich meal (white bread and processed cheese) decreased post meal energy expenditure in men and women by nearly 50% compared to a whole food cheese sandwich meal (whole grain and real cheese) [289]. All meals had similar calories and macronutrient contents. This means that people who ate real whole foods burned more calories than those eating processed foods. Their subjects also preferred the taste of the whole food cheese sandwich.

To compound the problem, people tend to eat more when consuming processed food. A small study of 20 adults found that people consumed 500 extra calories when eating highly processed foods than when eating minimally prepared whole foods [290]. In this study, both ultra-processed and unprocessed meals had the same amounts of calories, sugars, carbohydrates, fiber and fat. People were allowed to eat as little or as much as they liked. Those eating processed foods gained around 2 pounds while those eating whole foods lost 2 pounds [290]. Processed foods tend to reduce satiety while encouraging overconsumption.

6) Genetic variability should be taken into account when planning diets

Dietary studies are becoming more multicultural which is allowing narrower dietary recommendations. For example, people of recent African ancestry should reduce their consumption of omega-6 PUFAs due to their genetic tendency to have a super thrifty genetic variant of fatty acid desaturase. Blanket recommendations to substitute PUFA oils for SFAs may negatively affect their health.

Mohan et al. 2018 found a strong association between Asian-Indians consuming a high carbohydrate (65-75% carbohydrate) diet and T2D [298]. This association was greater when accompanied by obesity. Asians, but not Americans or Europeans, with higher concentrations of omega-3 in blood or diet had a 26% reduction in the risk of MetS [299].

A preliminary study reports that African ancestry may be an independent risk factor for oxidative stress and metainflammation which contributes to MetS [300]. African American umbilical vein endothelial cells had higher nitrate oxide (NO), interleukin-6 (IL-6), and lower superoxide dismutase activity, which is the major antioxidant defense system against reactive oxygen species (ROS). African American adults had higher plasma protein carbonyls, which are biomarkers of oxidative stress [301], and higher antioxidant capacity [300]. In addition, oxidative stress may independently contribute to insulin sensitivity among African American women when compared to European American women [302].

The majority of research on MetS so far has been done on people of European ancestry. More research is needed to account for the genetic variability of the over 80% of people that are not from European derived populations [303].

Diets to reduce MetS risk factors

It is impossible to make specific FA recommendations for broad groups of fats. However, it is possible to make general guidelines for a healthy diet based on current scientific knowledge:

1) Fats should comprise 25-40% of the diet:

People with metabolic syndrome or any of its risk factors such as T2D should consume more fats and/protein and a moderate carbohydrate diet (26-45% carbohydrate) (Hyde et al. 2019, 304, 285, 305].  

Eat whole food sources of fat; avoid fat in overly processed foods [88].

2) Fat quality matters:

Choose high quality fats found in whole foods such as olives, whole fat dairy, avocado, grass-fed beef, nuts, dark chocolate, egg yolks and seeds [94]. MetS and obesity are inversely correlated with nut consumption [306].

Use cold pressed and/or virgin oils which retain more antioxidants than refined oils. This prevents lipid oxidation and contamination; see Grajzer et al. 2020 for good discussion [307]. Cold pressed oils should be stored in the refrigerator and used quickly.

Avoid low quality refined fats. These are found in overly processed, bleached and deodorized oils as well as repeatedly heated oils such as those used in deep fat fried foods [291, 292]. 

Do not consume foods with industrially made TFAs. One study reported a dose-response increase in CVD with TFA consumption. Industrial TFAs confer a 30% increase in the risk of CHD events and an 18%

3) Choose the best fatty foods:

Add more MUFAs to your diet. MUFAs are found in olive oil, tree nuts, avocados, olives, red meat and peanuts.

Use full fat dairy which improves cardiometabolic health (Astrup et al. 2020).

Choose some foods that contain medium chain SFAs. These include coconut, vegetable oils, dark chocolate and whole fat dairy products [282].

Do not be afraid of SFAs. High quality SFAs are fine if not over eaten. There are many health benefits from short and medium chain SFAs. SFA foods include meats, animal fats, avocado, full fat dairy products, and dark chocolate [82, 83, 94]. 

*Names and some minor identifying details in all stories in this website are changed to protect people's privacy.

This information in this website is for informational purposes only and does not constitute medical advice, diagnosis, or treatment.

4) Your body cannot make PUFAs:

Add both omega-6 and omega-3 FAs foods to the diet.

To balance the omage-3 omega-6 ratio, try to consume more foods rich in omega-3 FAs and reduce foods high in omega-6 FAs; especially oils. Adding 3-4 grams of omega-3 FAs to the diet will lower TG and blood pressure [280].

Red meat is fine [309]. Choose organic and/or grass-fed beef if possible. Organic beef is 47% higher in omega-3 FAs than conventional beef. This is probably due to the fact that organic cattle are more likely to be pasture raised. Omega-3 FAs are higher in meats from grass fed ruminants; ground beef from grass fed steers contains 676 α-linolenic acid/100 g total fatty acids compared to 207 mg α-linolenic acid/100 g total fatty acids in ground beef from grain-fed steers [310].

5) Your body makes SCFAs.

Make your own fatty acids by adding fiber rich foods to the diet [311, 312].

Foods that are rich in fiber; such as bananas, raspberries, carrots, peas, tomatoes and onions; contribute to SCFAs which are metabolically healthy. [60, 61, 59].

Butter, cheese and goat’s milk also contains SCFAs [53].

6) Take ethnicity, genetics and epigenetics into account.

People with a family history of metabolic disorders are more likely to have problems from over consumption of fats and sugars.

Genetic and epigenetic changes are involved in T2D [313]. Epigenetics can be influenced by environmental factors such as dietary fats [314].  

No diet is perfect for everyone.

By Lori Woods MS Human Nutrition and Susan Fluegel PHD Nutritional Biochemistry. Both of us feel strongly about developing guidelines for people to help prevent metabolic disorders such as T2D.

References:

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