Might we study one thing from the dietary habits of squirrels, significantly their penchant for acorns, which they depend upon to fatten up for the winter? In accordance with Brad Marshall, a molecular biologist, farmer and chef, the key to staying slim might lie within the historical relationship between squirrels and the oak bushes that give them their favourite meals supply.
“All mammals advanced from a standard ancestor. We’ve the identical enzyme techniques that management power steadiness out and in and though we dwell in several environments and we’ve completely different most popular meals, our metabolisms all primarily work the identical method,” Marshall says.1
Oak Bushes Make Acorns to Fatten Up Squirrels
You could assume that squirrels advanced to eat acorns with a purpose to acquire weight earlier than winter units in. However Marshall factors out that mammals have been round for at the very least 200 million years, whereas flowering crops like oak bushes and hickory bushes are comparatively a lot youthful, evolving round 130 million years in the past.
“I imagine that the bushes advanced to make use of mammals to maneuver their seeds round for them,” Marshall says.2 He cites a examine of untamed pink squirrels,3 which discovered their physique weight elevated from about 310 grams to 330 grams within the fall after they eat probably the most acorns.
“They’re primarily including about 10% of their weight in physique fats throughout the a part of the 12 months after they’re consuming these acorns and, after all, 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 may 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 … in case you are an oak tree and it is your crucial to fatten up your squirrels in order that they’ll survive winter so as to unfold your seeds, what do you make your acorns out of?”5
Black oak acorns, which squirrels choose, 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 bushes 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 displaying folks 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 rather a lot 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 referred to 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 examine this course of by utilizing particular mice fashions referred to as “knockout fashions,” the place particular genes are eliminated to see the results.
In research targeted on diet-induced weight problems, these mice are fed a weight loss program just like the composition of acorns, which is excessive in fats, primarily from lard and a few soybean oil.
This weight loss program 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); fashionable lard incorporates extra polyunsaturated fat (PUFAs) than it used to. The weight loss program for the mice consists of about 5% soybean oil to make sure there’s sufficient PUFA.
This weight loss program successfully causes weight acquire 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.
An identical course of happens in people after they’re given a drug referred to as fenofibrate, which additionally prompts PPAR-alpha. In a examine performed on males, researchers used fenofibrate to deliberately activate PPAR-alpha to check its results on the liver.9
Curiously, Marshall explains, whereas fenofibrate is efficient at reducing ldl cholesterol, this was the primary time researchers immediately 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 examine examined the exercise of two enzymes: delta-6 desaturase and delta-9 desaturase, often known as SCD-1. These enzymes play roles in fats metabolism, and their exercise ranges elevated considerably — by about 58% and 36%, respectively — in members whose PPAR-alpha was activated by fenofibrate. This improve in enzyme exercise additional signifies modifications 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 referred to 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 predominant pathways. One pathway includes conversion into acetyl coenzyme A (acetyl-CoA) by an enzyme referred to as pyruvate dehydrogenase, resulting in the tricarboxylic acid (TCA) cycle, a crucial step in power manufacturing from meals.11
Throughout this cycle, acetyl-CoA is damaged down, producing molecules referred to as nicotinamide adenine dinucleotide, or NADH. The supply 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 take care of metabolic steadiness.
One main technique is thru the electron transport chain within the mitochondria, which not solely regenerates NAD+ but additionally produces ATP, the power forex of the cell used for every little thing from shifting muscular tissues to mind features.
Nevertheless, not all power manufacturing goes easily. When there’s an extra of NADH and never sufficient demand for ATP, an enzyme referred to as pyruvate dehydrogenase can change into much less energetic, 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 through the TCA cycle. As a substitute, pyruvate takes an alternate route by an enzyme referred to as pyruvate carboxylase, favoring the manufacturing of a compound referred to as oxaloacetate.
This shift redirects the cell’s power processes, combining pyruvate from carbohydrates and acetyl-CoA from fat to create new fat by a course of referred to as de novo lipogenesis. Primarily, Marshall explains, the presence of PPAR-alpha, stimulated by fat within the weight loss program, influences your physique’s resolution 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 a very good 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 also 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 power, resulting in a choice for creating new fat slightly than simply burning carbohydrates for power.13
This course of includes a number of steps throughout the cell. Excessive ranges of NADH, which happen when PPAR-alpha is energetic, favor the conversion of gear within the cell in a method 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 gear related to weight problems.
The activation of PPAR-alpha and one other part referred to as cytochrome P450 1B1 additionally results in elevated exercise of an enzyme referred to as SCD1. This enzyme, together with others concerned in fats creation, ramps up your physique’s skill to make fats.
Because of this, sure fatty acid ranges change, selling the storage of fats over burning it for power. This mechanism slows down the metabolic charge, inflicting your physique to retailer extra energy as fats.
From the angle of an oak tree, this course of is good, Marshall says. By producing acorns that result in the storage of fats, oak bushes assist squirrels acquire the burden essential to survive the winter. This ensures the squirrels are able to disperse the oak’s seeds, serving to within the tree’s copy.
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 offers 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 must be under 5 grams a day.
The best method to do that is to make use of an internet dietary calculator similar to Cronometer to calculate your every day consumption. Cronometer will let you know 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 prone to trigger issues however, as talked about, I like to recommend protecting your consumption under 5 grams a day.
