The genes we developed to ensure our survival are now our burden in the age of abundance

Last week I gave a talk (Food for Thought: Facts and Myths of fat and Carbohydrate) to the Bible Class among Taiwanese community in the greater Pittsburgh area. I think I lost many in the first 5 minutes trying to convey difficult concepts based on evolutionary medical biochemistry to unravel the complexity of metabolism pathway. Along the way I clarified our understanding of fats and crabohydrates and their relationship to cardiovascular disease—not covered in this writing. As J. Robert Oppenheimer said, "I can make it clearer, I can not make it simpler." Here is my attempt to make it clearer.

When Mark Twain said, “Just eat it, let them fight it out inside,” he 'knew' the food we eat are glucose, amino acid, and fatty acid, which will find their way to be absorbed. And if you eat more than you burn, the left over will be stored (glucose is stored as glycogen, amino acid protein, fatty acid fat.)

Metabolism pathways
But, things are not this simple, the above is the simplified version of metabolism pathway showing glucose can become fat (triglyceride) and vice versa (the same can be applied to protein, which is not the topic of this writing) The entire system is fluid and dynamic; all roads lead to Rome, and all things lead to Acetyl CoA. Building up or breaking down of a molecule often leads to Acetyl CoA. This is either the God’s grand design or the evolution perfected it over the millions, nay, billions of years. This system makes the best use of the resource—one thing can be turned to another as the need changes.

Once we quit eating, glycogen (in the muscles) will be converted back to glucose, but that will only keep us going for a day or two and the only reason we can survive for weeks without food is the mobilization of fatty tissue to make glucose. Given the fact that 1 gram of fat-burning yields 9 calories, comparing to 4 for corresponding carbohydrate or protein, we would be at least twice our size to survive as long, were it not this ingenious system.

In response to fight-or-flight situation, adrenaline is running, leading to mass production of glucose (mediated by adrenaline) to ready the muscles and brain by promoting the steps making glucose and inhibiting steps away from it. One may survive hunger strike for weeks without the undue hypoglycemia (low blood sugar). When food supply stops, the system begins to convert fatty acids and amino acids (proteins) to glucose mostly in the liver.

Concept 1:: interconverting among various nutrients makes the best use of the resource.

I can simply give some straightforward recommendations saying saturated fats are bad, trans fats are even worse, and unsaturated fats and omega 3 fatty acids are protective. Too much sweet (carbohydrates) is as bad as not enough of it. That would defeat the purpose of giving a talk; everyone can search it online.

Many in the audience are physicians themselves and still many others hold or held academic positions at Pitt or CMU or Ph.D. candidate. So the audience are highly educated intellectuals and the topic of Food for Thought is figuratively and literally appropraite in provoking them to give it a thought whether it makes sense or not.

Many years ago Newsweek published my Letter to the Editor (talking about God and evolution) but the editor deleted a sentence of “The wonder, beauty, and complexity of evolution, especially at a molecular level, holds many students of evolution in awe.” Many, the educated included, still can not accept the evolution theory, let alone at the molecular level.

Evolution is just a scientific theory, which as Richard Feynman put it “the theory is so useful in understanding the way nature works that we can almost call it real.”

Studying medical biochemistry from the perspective of evolution is by no means original of my own. In a Biochemistry textbook, the authors (Jeremy Berg and Lubert Stryer) took every chance to use the evolution to better explain things.

It takes numerous pathways and steps to convert glucose to triglyceride (fat): glucose à à à à à à à à à à à à à triglyceride; each step requires an enzyme to expedite its chemical reaction. One gene one enzyme! each enzyme is the product of a gene.

Concept 2:: It is our genes that make the storage of energy efficient.

Our ancestors spent all their waking hours gathering food which was scarce. We needed then to store energy as much and as fast as we can to ensure survival. Over the long evolutionary history many genes were developed to make the storage of energy expedient and efficient and the expense of it economical. It took you 20 minutes to eat a Big Mac while sitting and biking, in the end you gained nearly 500 calories and burned about 50 calories only. The pathways and steps to produce energy (ATP) are so efficient and economical that burning one molecule of glucose yields more than 60 molecules of ATP.

Concept 3:: It is also our genes that make the expenditure of energy economical.

This is to say that the over-efficient genes we developed over the eons are not suitable for our age of affluence and abundance. We’re left with only one option: eat less, exercise more and go extra miles while biking or running.

This may be the reason why many seemingly different or even opposite diets (low fat, high CHO vs low CHO, high fat) all achieve somewhat similar results.

Concept 4:: It is not what types of food you eat, it is the total amount of food (calories) you consume that counts.

"Live sensibly--among a thousand people, only one dies a natural death, the rest succumb to irrational mode of living."

Admittingly many of the diseases we suffer through no fault of our own, but, general speaking the wisdom of Maimonides (the Middel Age Jewish physician and philosopher, 1135-1204) still stands today. We only need to change the 'mode of living' to 'life style.'