How Things Work: Food Energy

As media headlines have been telling us in the industrialized world for quite some time now, being overweight or obese greatly increases a person’s risk of heart disease, stroke, diabetes and other chronic diseases.

With rapid globalization these so-called western lifestyle problems are popping up at an astounding rate in almost every corner of the world. Over one billion people are overweight and if the trend continues, there will be half a billion more by 2015, according to the World Health Organization (WHO).

“The rapid increase of overweight and obesity in many low and middle income countries foretells an overwhelming chronic disease burden in these countries in the next 10 to 20 years if action is not taken now,” warns WHO’s Catherine Le Galès-Camus.

Source: OECD Health Data 2005 via Nation Master

The cause of the epidemic is pretty much the same in both the developed and developing worlds: at a time when urbanization is leading more of us to sedentary lifestyles, people are eating the wrong stuff on a regular basis.

“Globalization has made cheap oils, fats and sugars widely available in all nations, causing increases in fat and sugar intake worldwide. Industrialized agro-food systems established by global corporations have successfully increased access to cheap calorie-dense foods across the world,” nutritionist Maria de Lourdes Alvarez told us.

“Fast food chains and vending machines packed with lipid-sugar-rich foods as well as high calorie soft drinks can now be found in the most remote corners of the world,” said Alvarez, who is finishing her Masters (specialized in diabetes prevention) at McGill University in Montreal, Canada.

Disturbingly, children may bear a large brunt, as new studies show they are reaching puberty earlier and are at risk of dying young.

“Health care professionals now acknowledge that childhood obesity/overweight is such that we could be seeing, for the first time in human history, the possibility of millions of parents outliving their children,” Alvarez said.

“Childhood obesity is already epidemic in some areas and on the rise in others. An estimated 22 million children under five are estimated to be overweight worldwide.”

Bad for you, bad for the Earth

Meanwhile, the majority in affluent countries could choose to eat properly yet seem incapable of reversing this trend. Some say the food industry is purposely enabling addictions that are bad for us, like Big Tobacco did.

Regular readers of Our World will not be unfamiliar with the questions concerning industrialized food systems. They might have read about calls by some, like food author Michael Pollan, that we need to reject the “nutrionalization” of food, to give up eating processed “food-like substances” entirely and stick with eating whole foods.

Certainly it seems that food science (and its corresponding influence on our dietary habits) has taken some serious wrong turns, one of which is evidenced by the recent revelation that it’s not fat that is making us fat but refined carbohydrates. If you follow a lot of food info as we do, that particular revelation will ring quite true, bringing to mind the documentary King Corn about the corn/corn syrup industry in the United States.

Moreover, those of us who can afford to rethink what we eat have yet another reason to so: the stuff that fattens our waistlines tends to also have the heaviest carbon footprints. Indeed it seems that ideas formerly viewed as quite “radical” like veganism (a diet free of animal products), are struggling to go mainstream. Even the UN Environment Programme in June published a report that says a global shift towards a vegan diet is vital to saving the world from hunger, resource depletion and the worst impacts of climate change.

In the end, no matter which side of the meat-climate issue you take, ignorance of the consequences of your eating habits is definitely dangerous to one’s own health as well as to that of the planet — which is precisely why we thought this primer couldn’t hurt.

Getting your head around your metabolism

As primal as they may feel, hunger pangs, the actual act of eating and the ultimate generation of the energy that keeps you alive are all part of a complicated system of chemicals and signals between brain and body.

The breakdown products of the foods you consume — glucose from carbohydrates, amino acids from protein, and fatty acids from fat — form part of a potion that activates hormones like insulin and kicks the body’s food energy-making machine into action.

Metabolism is basically defined as the series of chemical processes that convert food (and oxygen) into the energy and products needed to sustain life.

One way to understand metabolism is to track a typical nutrient on its journey through the body. A nutrient is any substance that helps an organism stay alive, remain healthy, and grow.

The three overarching categories of macronutrients are carbohydrates, proteins, and fats. Understanding them is key to getting things balanced, making sure you are running your machine with the optimal fuel for your health (and the planet’s).

Carbohydrates (saccharides)

This is the category of nutrient upon which the majority of the world’s dietary guideline pyramids are based. The Food and Agriculture Organisation recommends 55% of food energy be derived from a variety of carbs. (We’ve added emphasis there because that is where a majority of people are going wrong.)

Source: © 2008 President and Fellows of Harvard College via Flickr.

However, it is also the most misunderstood, and these days abused, nutrient type! Most people know that cereal-based, starchy and sugary foods — and beverages like soda pop and fruit drinks — are carbohydrates, but it seems many don’t realize that the category also includes legumes (like lentils and beans), vegetables and fruits.

Carbohydrates have often been classified as “simple” or “complex” because, while all types are composed of units of sugar, some carbs are made up of a larger number of units or of units that are more closely bound together and so require more processing by our bodies to convert them into simple sugars that can be absorbed into the bloodstream.

As the sugar level rises in your blood, that familiar hormone called insulin does its job telling the blood sugar (glucose) to move into the cells, to be used for generating energy. When this process goes slow — like with complex carbs from whole-grain food — you’ll feel satisfied longer and have energy over a longer period of time. When it goes fast, as with simpler carbs, you’re more likely to feel hungry again soon.

The speed of effect on glucose levels is why most scientists prefer referring to foods as either provoking low or high “glycaemic response” or  by “glycaemic index”. (A quick example: a doughnut has an index of 75, where an apple’s is 41.) Eating a lot of high glycaemic index carbohydrates has a “yo-yo effect on blood glucose” and research is proving that this contributes to weight gain and the promotion of diabetes and heart disease.

Dietary fibre is a key factor in this equation. Eating a diet full of food made from grains that have been processed/refined to remove the more fibrous parts (eg., white flour) and products with added sugar means not only that your glucose levels are messed up and you are likely overeating, but that beneficial bulk (which protects you from colorectal diseases), vitamins, minerals and other macronutrients are stripped out.

[quote quote=”Whole grains contain the entire grain – the bran, germ and endosperm.” type=”image” image=”2316″ ] Photo by: International Rice Research Institute.

For those most familiar with sweet pastries and white bread, some examples of fibre-rich whole grains include brown rice, buckwheat, bulgur, millet, quinoa, whole oats, whole grain wheat and wild rice. These staples are things with which it would be wise to acquaint yourself, along with the gold star carbs — fruits and veg.


Protein, we all know, is another vital macronutrient. It is made up of building blocks called amino acids, most of which are used by your body to make things like enzymes, hormones, antibodies and tissue proteins like muscle.

Not all dietary proteins contain all the amino acids the body needs. Nutritionists classify amino acids as essential or nonessential — essential means they can’t be synthesized by your body and need to come from food. Of the 22 different amino acids needed by the body, eight are considered essential for adults.

Some protein sources are considered to be more complete or of a ‘higher quality’ than others, based on the ratio of protein to amino acids they contain. Eg., eggs may contain a lower percentage of protein than lentils, but the proteins in lentils don’t provide as much of the essential amino acids, so are not as nutritionally complete as eggs.

However, the protein myth is just that — humans do not biologically need to eat meat.

“A well-planned vegetarian diet can provide adequate amounts of all the nutrients a person needs for good health,” says Alvarez. “Vegetarians who include milk products and eggs can meet recommendations for most nutrients about as easily as non-vegetarians. Such diets provide enough energy, protein, and other nutrients to support the health of adults and the growth of children and adolescents.”

“Conversely, both vegetarian and meat-based diets can be detrimental to health when overloaded with fat and simple sugar… And both diets, if not properly balanced, can lack nutrients. Poorly planned vegetarian diets typically lack iron, zinc, calcium, vitamin B12 and vitamin D; without planning, the meat eater’s diet may lack vitamin A, vitamin C, folate, and fibre, among others.”

Even the United States Department of Agriculture has recognized in the recently released Report of the Dietary Guidelines Advisory Committee the beneficial impacts of plant-based protein sources. Though of course this year’s revised Guidelines risk being ignored and lobbied against by special interest groups (like salt and supplement companies), as was the case for the 2005 version.

Source: The Vegetarian Resource Group

When it comes to how much protein a body needs, opinions can vary. Harvard’s School of Public Health and many others quote the Institute of Medicine’s recommendation that adults get a daily minimum of 0.8 grams of protein for every kilogram of body weight — about 64 grams for a 73 kg (160 lb) adult. There are others who argue that it should be more, depending on your metabolism and or activity level. If you’re a calorie-counter, Alvarez counsels that 10-35% of daily calories should come from protein.

Fats (lipids)

While industrialized societies have seen the demonization of fats, they actually have a really important role to play in our metabolism. Though if you haven’t been scared into the fat-free mindset and you do allow fats in your diet, it can be a challenge getting the right fats, due to the prevalence of bad ones in today’s processed foods.

“Fat helps the body use its two other energy nutrients — carbohydrate and protein — efficiently,” Alvarez explains. “Fat fragments combine with glucose fragments during energy metabolism and fat helps spare protein, providing energy so that protein can be used for other important tasks.”

“Most people should consume at least 15 percent of their energy intake from fat — the recommended intake range is 20-30%,” she advises. “Overweight or obese people usually consume more than 30 percent of their daily energy intake [from fat]”.

This habit may be partly due to chemicals that control appetite (researchers have identified 12) and the sensation of fullness (satiation), or it might be more of an environmental (psychological) response.

Alvarez says neuroimaging studies show that good smelling, looking or tasting food affects our brain in a similar way as drug abuse. “Many of the brain changes reported for hedonic eating and obesity are also seen in various forms of addictions,” she said.

“Most importantly, overeating and obesity may have an acquired drive like drug addiction with respect to motivation and incentive; craving, wanting, and liking occur after early and repeated exposures to stimuli.”

While the concrete cause is elusive, some research is yielding news you can use.

“Researchers have developed a satiety index of common foods. In doing so, they confirmed that the satiating effect of fat is weak and that of protein and fibre is strong. High-fat foods such as croissants, doughnuts, peanuts, and potato chips please the palate and stimulate the appetite, but score low on the satiety index.”

It is all a matter of balance

We hope you have been able to easily digest this primer and that you are inspired to take your metabolism into your own hands and feed your body what it deserves! One final and important reminder is that it is extremely important to strive for “energy balance”.

“The obesity epidemic is a combination of multiple factors that all contribute to exacerbate the problem,” Alvarez explains. “At the most fundamental level, overweight and obesity result from an imbalance between caloric intake and expenditure of energy.”

The majority of people who are overweight or obese are eating more (mostly empty, unsatisfying and vitamin-lacking) calories than their bodies can use. However, those of us in affluent countries need not fear going hungry in order to correct that imbalance — we are in the lucky position of simply needing to readjust our diets and begin eating foods that are more satisfying and less processed and/or sugary.

Which, with a little effort, can become as easy as (whole-wheat crusted spinach) pie!

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How things work: Food energy by Carol Smith is licensed under a Creative Commons Attribution-NoDerivs 3.0 Unported License.


Carol is a journalist with a green heart who believes that presenting information in a positive and accessible manner is essential to activating more people to join the search for equitable and sustainable solutions to global problems. A native of Montreal, Canada, she joined the UNU communications team in 2008 while living in Tokyo and, after relocating to Vancouver, continued to telecommute to Our World as writer/editor through 2015.