Might we study one thing from the dietary habits of squirrels, significantly their penchant for acorns, which they rely upon to fatten up for the winter? In keeping with Brad Marshall, a molecular biologist, farmer and chef, the key to staying slim could lie within the historic relationship between squirrels and the oak timber that give them their favourite meals supply.
“All mammals advanced from a typical ancestor. We’ve the identical enzyme programs that management vitality steadiness out and in and despite the fact that we stay in several environments and now we have completely different most popular meals, our metabolisms all basically work the identical manner,” Marshall says.1
Oak Bushes Make Acorns to Fatten Up Squirrels
You might assume that squirrels advanced to eat acorns with a purpose to achieve weight earlier than winter units in. However Marshall factors out that mammals have been round for a minimum of 200 million years, whereas flowering crops like oak timber and hickory timber are comparatively a lot youthful, evolving round 130 million years in the past.
“I consider that the timber advanced to make use of mammals to maneuver their seeds round for them,” Marshall says.2 He cites a research of untamed pink squirrels,3 which discovered their physique weight elevated from about 310 grams to 330 grams within the fall once they eat essentially the most acorns.
“They’re basically including about 10% of their weight in physique fats throughout the a part of the 12 months once they’re consuming these acorns and, in fact, from the angle of the tree, the tree wants these squirrels to fatten up. The tree wants a wholesome squirrel inhabitants in order that it could actually unfold its seeds and so that is what squirrels eat.”4
Within the fall, acorns and hickory nuts make up 90% of squirrels’ diets. This falls to about 50% to 63% in the summertime, when squirrels are their leanest. Marshall poses the query:
“So … if you’re an oak tree and it is your crucial to fatten up your squirrels in order that they will survive winter so to unfold your seeds, what do you make your acorns out of?”5
Black oak acorns, which squirrels want, include about 46% of energy from fats, 48% of energy from carbohydrates and 6.6% of energy from protein. “That’s the equation that the oak timber determined to make use of.”6
The acorns, together with hickories and chestnuts, are very low in saturated fats with very excessive quantities of monounsaturated fats and “fairly a little bit of polyunsaturated fats together with starch within the acorns. That appears to be the recipe that’s most popular,” Marshall factors out.7 Within the video, he then reveals information exhibiting individuals in France, who eat extra butter and dairy fats, are leaner than these in Italy and Spain, the place olive oil is favored.8
Why Acorns Make Squirrels Fats
A squirrel digesting an acorn can educate us lots about fats digestion and its results on the physique. When a squirrel eats an acorn, its physique breaks down the fat it incorporates. Throughout this course of, the squirrel’s intestines launch a substance known as oleoylethanolamide (OEA). OEA acts as a sign telling the physique that fat are being digested.
As soon as OEA enters the bloodstream, it triggers a response within the liver by activating a receptor often called PPAR-alpha. This activation begins the method of fats accumulation within the physique. Researchers research this course of through the use of particular mice fashions known as “knockout fashions,” the place particular genes are eliminated to see the results.
In research centered on diet-induced weight problems, these mice are fed a food plan just like the composition of acorns, which is excessive in fats, primarily from lard and a few soybean oil.
This food plan mirrors the fatty content material of acorns and is designed to induce weight problems and insulin resistance in mice. An vital level is that lard is principally composed of monounsaturated fat (MUFAs); trendy lard incorporates extra polyunsaturated fat (PUFAs) than it used to. The food plan for the mice consists of about 5% soybean oil to make sure there’s sufficient PUFA.
This food plan successfully causes weight achieve and insulin resistance in mice. The research present that having the PPAR-alpha receptor is essential for the mice to develop insulin resistance, providing insights into how fat have an effect on the physique’s metabolic processes.
The same course of happens in people once they’re given a drug known as fenofibrate, which additionally prompts PPAR-alpha. In a research performed on males, researchers used fenofibrate to deliberately activate PPAR-alpha to review its results on the liver.9
Curiously, Marshall explains, whereas fenofibrate is efficient at reducing ldl cholesterol, this was the primary time researchers instantly noticed its affect on the liver in people. The outcomes confirmed that fenofibrate elevated liver fats content material by about 23%, which means that activating PPAR-alpha can have unintended results on the physique’s fats storage processes.
Moreover, the research examined the exercise of two enzymes: delta-6 desaturase and delta-9 desaturase, also called SCD-1. These enzymes play roles in fats metabolism, and their exercise ranges elevated considerably — by about 58% and 36%, respectively — in individuals whose PPAR-alpha was activated by fenofibrate. This enhance in enzyme exercise additional signifies adjustments in how the physique processes and shops fat.10
The importance of those findings lies within the connection to MUFA, like these present in acorns. The presence of MUFA can provoke the activation of PPAR-alpha, showcasing its position as a key regulator in fats metabolism.
What This Means for Human Metabolism
When glucose from meals like acorns enters a cell, it undergoes a course of known as glycolysis within the cell’s cytoplasm, changing into pyruvate. This pyruvate then strikes into the mitochondria, the cell’s powerhouse, the place it has two fundamental pathways. One pathway includes conversion into acetyl coenzyme A (acetyl-CoA) by an enzyme known as pyruvate dehydrogenase, resulting in the tricarboxylic acid (TCA) cycle, a vital step in vitality manufacturing from meals.11
Throughout this cycle, acetyl-CoA is damaged down, producing molecules known as nicotinamide adenine dinucleotide, or NADH. The provision of one other molecule, NAD+, is essential right here as a result of a scarcity can decelerate metabolism. Your physique has mechanisms to transform NADH again to NAD+ to keep up metabolic steadiness.
One main methodology is thru the electron transport chain within the mitochondria, which not solely regenerates NAD+ but additionally produces ATP, the vitality forex of the cell used for all the things from shifting muscular tissues to mind capabilities.
Nevertheless, not all vitality manufacturing goes easily. When there’s an extra of NADH and never sufficient demand for ATP, an enzyme known as pyruvate dehydrogenase can turn into much less lively, resulting in the manufacturing of reactive oxygen species (ROS), like hydrogen peroxide. One other enzyme, NNT, helps convert this probably dangerous byproduct again into water, concurrently changing NADH again to NAD+.
However, when PPAR-alpha, activated by the MUFAs from acorns, comes into play, it inhibits pyruvate dehydrogenase by activating a distinct enzyme, pyruvate dehydrogenase kinase. This motion prevents the traditional breakdown of pyruvate by way of the TCA cycle. As a substitute, pyruvate takes an alternate route by means of an enzyme known as pyruvate carboxylase, favoring the manufacturing of a compound known as oxaloacetate.
This shift redirects the cell’s vitality processes, combining pyruvate from carbohydrates and acetyl-CoA from fat to create new fat by means of a course of known as de novo lipogenesis. Basically, Marshall explains, the presence of PPAR-alpha, stimulated by fat within the food plan, influences your physique’s choice to transform carbohydrates into fats.
Why Diets Excessive in Linoleic Acid Are Fattening
Acorns from pink or black oaks are a mixture of fat and carbohydrates, with their fats content material being principally monounsaturated and portion of it being linoleic acid (LA), a PUFA.
LA accounts for about 80% of the fats composition of vegetable/seed oils. Examples of seed oils excessive in omega-6 LA embrace soybean, cottonseed, sunflower, rapeseed (canola), corn and safflower.12
Marshall explains that the presence of oleic acid, one other part of the fats in acorns, can be vital as a result of it triggers a response within the liver that prompts PPAR-alpha. As soon as activated, PPAR-alpha influences how the cell makes use of vitality, resulting in a choice for creating new fat relatively than simply burning carbohydrates for vitality.13
This course of includes a number of steps throughout the cell. Excessive ranges of NADH, which happen when PPAR-alpha is lively, favor the conversion of drugs within the cell in a manner that results in fats manufacturing. Particularly, delta-6 desaturase converts LA to arachidonic acid, which performs a task in creating molecules that may set off reactions resulting in the manufacturing of drugs related to weight problems.
The activation of PPAR-alpha and one other part known as cytochrome P450 1B1 additionally results in elevated exercise of an enzyme known as SCD1. This enzyme, together with others concerned in fats creation, ramps up your physique’s capacity to make fats.
Consequently, sure fatty acid ranges change, selling the storage of fats over burning it for vitality. This mechanism slows down the metabolic price, inflicting your physique to retailer extra energy as fats.
From the angle of an oak tree, this course of is right, Marshall says. By producing acorns that result in the storage of fats, oak timber assist squirrels achieve the load essential to survive the winter. This ensures the squirrels are able to disperse the oak’s seeds, serving to within the tree’s replica.
This intricate connection between the composition of acorns and the metabolic processes in animals that eat them illustrates an interesting facet of pure symbiosis that additionally provides clues to human weight problems.
In brief, Marshall notes, “Black and pink oak acorns have advanced to be completely fattening,”14 and so, too, have the modern-day diets that mimic them, that are very low in saturated fats with very excessive quantities of MUFA, and PUFA like LA.15 Ideally, your consumption of LA needs to be beneath 5 grams a day.
The best manner to do that is to make use of a web-based dietary calculator akin to Cronometer to calculate your each day consumption. Cronometer will inform you how a lot omega-6 you’re getting out of your meals right down to the tenth of a gram, and you may assume 90% of that’s LA. Something over 10 grams is more likely to trigger issues however, as talked about, I like to recommend preserving your consumption beneath 5 grams a day.
