Fat. Viewed over the years as both hero and villain, fat has been the subject of dietary debate since physiologist Ancel Keys presented a hypothesis linking saturated fats and heart disease at a 1955 meeting of the World Health Organization.\u00a0<\/p>\n
Revised\u00a0Dietary Guidelines for Americans<\/a> issued late last year by the U.S. Department of Health and Human Services and the Department of Agriculture and updated\u00a0Dietary Guidance to Improve Cardiovascular Health<\/a> published by the American Heart Association (AHA) in March 2026\u00a0have only added sizzle to the discussion.\u00a0<\/p>\n The facts around fat can seem bewildering\u2014but Tufts experts<\/a> are helping make sense of them. Diane McKay, assistant professor at the Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy<\/a>, helped Tufts Now sort out six common assertions.<\/p>\n First, what are fats and how do they work?<\/p>\n Fats (technically called lipids), along with proteins and carbohydrates, constitute one of three macronutrients required for our bodies\u2019 most basic functions, like energy, growth and tissue repair. Fats yield more than twice as many calories per gram as carbs or protein, so fatty foods are favorites with human and non-human animals, who instinctively seek energy-rich foods.\u00a0<\/p>\n Ninety-five percent of the fats in our bodies and in our food are triglycerides, so-called because they\u2019re composed of a molecule called glycerol attached to three fatty acids\u2014basically chains of carbon atoms bonded to one another and to varying numbers of hydrogen atoms as well. The structure of the fatty acids determines if the fat is categorized as saturated, monounsaturated or polyunsaturated.\u00a0<\/p>\n If a fatty acid\u2019s carbon atoms are fully bonded with hydrogen, it\u2019s considered saturated. Saturated fatty acid chains are straight. As a result, they readily align to form rigid structures that, for example, contribute to healthy cell membranes. Saturated fats are typically solid at room temperature\u2014think of butter or the marbling in a steak.\u00a0<\/p>\n If one or more carbon atoms in a chain are not fully bonded with hydrogen, that fatty acid is considered monounsaturated or polyunsaturated. Unsaturated fatty acid chains are kinked, making them more fluid than their saturated counterparts. Liquid oils at room temperature, unsaturated fats are found in fish and seafood and plants like nuts, avocados and seeds.\u00a0<\/p>\n Most fats actually contain a combination of different fatty acids, with one predominating, and good health requires a balance of fatty acids.<\/p>\n Common belief #1: Saturated fat is always an unhealthy nutrient, for everyone.\u00a0\u00a0<\/p>\n Not exactly, said McKay. Everyone\u2019s body includes some saturated fat, and saturated fats play an important role in cell membrane structure and hormone production. However, our bodies can synthesize such fats so we don\u2019t have to get them from food. The two essential fats that we must consume through diet because our bodies can\u2019t produce them are the polyunsaturated fats alpha-linolenic acid and linoleic acid.\u00a0<\/p>\n But problems arise when we consume more saturated fat than our body needs. Excess saturated fat reduces the body\u2019s ability to remove low density lipids (LDL) from the blood, which can lead to atherosclerosis (clogged arteries). In contrast, when substituted for saturated fatty acids in the diet, both monounsaturated and polyunsaturated fats have similar effects on lowering total and LDL cholesterol in our blood.\u00a0<\/p>\n And, although dietary fat doesn\u2019t appear to initiate cancers, said McKay, it can promote development once cancer has started; prostate cancer, for example, appears to be correlated with dietary fat intake, particularly from animal-based foods. Some research also links excess saturated fat with increased inflammation, which can be an early step in cardiovascular disease processes.<\/p>\n At the same time, evidence is emerging that saturated fat from certain dairy and fermented foods\u2014such as aged cheeses, yogurt, and kefir\u2014may be neutral or even beneficial when it comes to health, possibly due to beneficial compounds created during fermentation and aging.\u00a0<\/p>\n The latest AHA dietary guidelines note that there is some evidence that certain saturated fats may reduce cardiovascular disease mortality, but concludes that evidence for benefits of saturated fats is still limited across the board.\u00a0<\/p>\n \u201cMost qualified experts and research scientists would agree that consuming a higher proportion of unsaturated fats from varied sources, including plants, oils, and seafood, is more compatible with positive health outcomes when compared with excessive consumption of saturated fats,\u201d said McKay.\u00a0<\/p>\n A good guideline is limiting saturated fats to 6 to 10% of your daily calories and total fats to 20 to 35%.<\/p>\n Belief #2: Full-fat dairy can be good, particularly for kids.\u00a0<\/p>\n Yes. Although it\u2019s difficult for children under a year old to digest protein in cow\u2019s milk, the American Academy of Pediatrics recommends full-fat (whole) dairy for children between one and two years of age. \u201cThat\u2019s the critical stage when kids need lots of energy for rapid growth and neurological development,\u201d said McKay.\u00a0<\/p>\n In addition to calories, full-fat dairy products are a good source of nutrients that are particularly important during this growth period, including protein, calcium, phosphorus, potassium, riboflavin, and vitamins A, D, and B12. McKay noted that although there are a lot of high-fat foods available, not many are also a significant source of the nutrients essential to building healthy bones and supporting the development of other vital organs and systems.\u00a0<\/p>\n After age two, children can transition to reduced or non-fat dairy depending on their energy needs and family history of obesity or heart disease. While removal of fat from dairy decreases its fat-soluble vitamins, in the U.S. vitamins A and D are typically added back to milk during processing. The comparative benefits of full-fat, reduced-fat, low-fat and fat-free dairy for older children and adults continue to be studied\u2014and debated.\u00a0<\/p>\n Belief #3: Red meat can have a place in a healthy diet.\u00a0<\/p>\n Yes, in moderation. While red meat is higher in saturated fat than poultry or fish, McKay pointed out that red meat is also a great source of readily bioavailable iron and zinc. \u201cNothing says you have to eliminate every single bit of saturated fat from your diet,\u201d she said. But those who choose to eat red meat should limit portion size and frequency\u2014no more than three portions per week (each 4 to 6 ounces when cooked)\u2014and choose lean cuts of meat. \u00a0<\/p>\n Belief #4: \u201cNatural foods\u201d\u2014including red meat and butter\u2014are always better than \u201cultra-processed\u201d foods.\u00a0<\/p>\n Just because it\u2019s natural doesn\u2019t necessarily mean it\u2019s good for you, said McKay. Poisonous mushrooms, for example, are natural but they\u2019re not preferable to canned. There\u2019s not yet a standardized definition of \u201cultra-processed.\u201d Minimal processing such as canning, pasteurizing, freezing, or cooking can make food safer and fresh for longer, but consumers should moderate their intake of meats, including seafood, that have been smoked, cured, or salted, or that contain ingredients added to enhance flavor or appearance. When it comes to butter, McKay suggested substituting olive oil or another unsaturated vegetable oil for cooking and adding butter (if you choose) via a small pat either in the pan or on the food itself.<\/p>\n Belief #5: No more than 10 percent of our daily calories should come from saturated fat.\u00a0<\/p>\n The 10 percent guideline for saturated fat is a well-established number, said McKay. It continues to be the recommendation of the most recent national dietary guidelines as well those of the AHA. Overall, fats should make up no more than 35 percent of our calories. More research is needed before revising these numbers.<\/p>\n Belief #6: Animal fats can be just as healthy as plant fats.<\/p>\n It all depends on the animals and the plants, said McKay. The fatty acid profile of fish\u2014containing less saturated fat than beef and rich in polyunsaturated omega-3 fatty acids\u2014is healthier than the oils from tropical plants such as coconuts and palms, which are very high in saturated fats. Plus, fats aren\u2019t the only factor in the healthfulness of a food. Case in point: along with healthy fats, plants usually provide more fiber than animal foods; examples include avocados, nuts, and whole olives.<\/p>\n McKay added that we\u2019re moving into an age of precision and personalized nutrition that explores varied individual responses to different foods and nutrients. \u201cWe\u2019ve already seen these variations in response to carbohydrate-rich foods and that may turn out to be true of fats as well,\u201d she said.\u00a0<\/p>\n Meanwhile, moderation\u2014neither overindulging in one nutrient or food group, nor trying to cut one out entirely\u2014continues to be the foundation of a sensible approach to fats and overall dietary health.\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"Fat. Viewed over the years as both hero and villain, fat has been the subject of dietary debate…\n","protected":false},"author":2,"featured_media":723553,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[36],"tags":[64,63,137,532],"class_list":["post-723552","post","type-post","status-publish","format-standard","has-post-thumbnail","category-nutrition","tag-au","tag-australia","tag-health","tag-nutrition"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/723552","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=723552"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/723552\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/723553"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=723552"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=723552"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=723552"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}