The Science of Diet and Exercise

by Scientific American

For decades, experts reduced weight loss to simple math: burn more calories than you consume, without too much regard for what you consumed. Another old maxim presupposes that people who are more physically active burn more calories than less active people. Both tenets sound inescapably logical, but evidence is starting to refute such conventional wisdom on weight loss. Data from Susan B. Roberts and Sai Krupa Das show that the kinds of foods you eat are as important as how much you eat, and anthropologist Herman Pontzer’s studies of physically active hunter-gatherers illustrate that energy expenditure (caloric burn) stays virtually constant, regardless of activity. The eight articles in this collection present the most recent research examining the details of the metabolic process and testing new approaches, some of which can be applied to how we think about diet and exercise today.

Genres: Nonfiction

ebook

Published February 5, 2018

About the author

Scientific American , as an institutional author, is a popular science magazine founded by Rufus M. Porter and controlled by Nature Publishing Group since autumn, 2008. Mariette DiChristina has been editor-in-chief since December, 2009.

Reviews

[Kamila · Rating 4 out of 5]

Excellent resource with a lot of important, useful information, for just $6 from Scientific American's website.

Interesting points & key takeaways:

- Meat is difficult to obtain, and sharing more predictable plant foods is what allows hunting and gathering to work. Hunter-gatherer populations today get roughly half their daily calories from plants.
- Simply moving up the food chain means food is harder to find; there are a lot more plant calories on the landscape than animal calories.
- Evolution has a great memory but no plans. ... Evolution is not trying to get anywhere. We were not inevitable.
- Exercise causes the release of neurotrophic molecules that promote neurogenesis and brain growth.
- Exercise is not optional; it is essential, and weight loss is probably the one health benefit it largely fails to deliver. Our bodies are evolved to require daily physical activity.
- Physical activity has little effect on daily energy expenditure (Hadza hunter-gatherers burn the same number of calories every day as sedentary Westerners), which is one reason exercise is a poor tool for weight loss. Instead exercise regulates the way the body spends energy and coordinates vital tasks.
- Volume [of exercise] matters more than intensity.
- Humans tend to burn the same number of calories regardless of how physically active they are. ... [There are] no differences in daily energy expenditure between populations, despite large differences in activity levels.
- Even light activity, such as standing instead of sitting, causes muscles to produce enzymes that help to clear fat from circulating blood.
- "evolutionarily informed life"
- Exercise to stay healthy and vital; focus on diet to look after your weight.
- Sharing food is so fundamental to the human experience...that we take it for granted, but it is a unique and essential part of our evolutionary inheritance. Other apes do not share.
- Exercise is not the most important thing to focus on when you want to lose weight—although it has numerous other health benefits, including maintaining a healthy weight. ... What you eat and how much you eat play a substantially greater role in determining whether you shed kilograms.
- Different people lose weight more effectively with different foods.
- Humans do not need a lot of calories to stay healthy and active. And any excess consumption quickly results in weight gain. ... An excess of as little as 50 to 100 calories a day—the equivalent of one or two small cookies—can lead to a gain of one to three kilograms a year.
- Metabolism changes over time [and] when it comes to metabolic rate—and your ability to lose or maintain your weight—parentage makes a difference.
- From the standpoint of paleoecology, the Paleolithic diet is a myth. Food choice is as much about what's available to be eaten as it is about what a species evolved to eat.
- There is little doubt that dietary versatility has been key to the success we've had.
- Eating also lights up our reward circuitry. ... Researchers have found that for rats, sweetness surpasses even cocaine in its desirability. ... Food's effects on the reward system can override fullness and motivate us to keep eating.
- Over 90% of our body's serotonin is produced in the gut.
- Dieting does not promote lasting weight loss. ... When I say "diet," I am referring to eating regimens that require cutting portions, severely restricting calories, or eliminating entire food groups: carbs, fats, sweets, whatever. ... My advice as a psychologist and researcher who focuses on weight control: Do not diet. Do not cut out groups of foods or count calories. Do not try to eat very little or deprive yourself. ... Making small changes to your eating patterns, ones you can build on slowly over time, is truly the best pathway to lasting weight loss.
- Best tactics [included] self-monitoring, such as limiting certain foods, keeping track of portion sizes, planning meals, and incorporating exercise into the daily routine.
- For a species that evolved to consume energy-dense foods in an environment where famine was a constant threat, losing weight and staying trimmer in a modern world of plenty fueled by marketing messages and cheap empty calories is, in fact, terrifically difficult.
- The behavioral approach, tested over decades, involves making many small, sustainable adjustments in eating and exercise habits that are prompted and encouraged by the people and the rest of the environment around us.
- For most people with mild to moderate depression, exercise is one of the strongest, safest, most practical, most affordable and even enjoyable treatments available. ... Exercise enhances the biochemical effects of antidepressant drugs.

[Glenn V. · Rating 3 out of 5]

Consists entirely of reprints of recent articles from Scientific American and its sister publications about a handful of aspects of diet and exercise. I learned more than a little but I was really hoping for something more comprehensive.

[Lloyd Downey · Rating 2 out of 5]

I guess the thrust of this collection of articles from Scientific American could be summarised in a few sentences; basically they are saying that it’s really hard to lose weight and keep it off by exercising and people who work really hard don’t burn many more calories than a couch potato. And dieting is not easy for a whole host of psychological and biochemical reasons. In both cases, the underlying recommendation is to make small changes but stick to the regime. One thing that I did find missing in this book was any discussion of a change to a vegetarian diet or whole plant based food diet as recommended by T Colin Campbell. In fact, most of the diet changes discussed seem to be related to single constituent changes....like low carbs or high protein. etc. Each article is written by a different writer (or several writers).
Overall. I was not greatly impressed. I don't think I learned much that was new...a few things certainly....but it is pitched at a fairly low level of knowledge and there is no evidence there of any disagreements with the modest changes approach. No debate. A bit disappointing. Here are a few extracts that grabbed my attention:

1.1 The Exercise Paradox
Researchers in public health and human evolution have long assumed that our hunter-gatherer ancestors burned more calories than people in cities and towns do today. Given how physically hard folks such as the Hadza work, it seems impossible to imagine otherwise.....Hadza men ate and burned about 2,600 calories a day, Hadza women about 1,900 calories a day—the same as adults in the U.S. or Europe. We looked at the data every way imaginable, accounting for effects of body size, fat percentage, age and sex. No difference. How was it possible? What were we missing? What else were we getting wrong about human biology and evolution?
Comparing energy expenditure and physical activity in rural Nigerian women with that in African-American women in Chicago. [The survey] found no differences in daily energy expenditure between populations, despite large differences in activity levels. ...In 2013 Australian researchers found similar energy expenditures in sheep and kangaroos kept penned or allowed to roam free.
On average, couch potatoes tended to spend about 200 fewer calories each day than people who were moderately active: the kind of folks who get some exercise during the week and make a point to take the stairs......People with the most intensely active daily lives burned the same number of calories each day as those with moderately active lives. All of this evidence points toward obesity being a disease of gluttony rather than sloth. People gain weight when the calories they eat exceed the calories they expend.
Evidence indicates that it is best to think of diet and exercise as different tools with different strengths. Exercise to stay healthy and vital; focus on diet to look after your weight.
Our brains are so large that, as you sit reading this article, the oxygen from every fourth breath you take is needed just to feed your brain.
We had found in that study that primates burn only half as many calories a day as other mammals do......The reduced metabolic rates of primates correspond with their slow rates of growth and reproduction.......Sure enough, humans burn more calories each day than any of our great ape relatives. Even after accounting for effects of body size, activity level and other factors, humans consume and expend about 400 more calories a day than chimpanzees and bonobos do; differences with gorillas and orangutans are larger still. Those extra calories represent the extra work our bodies do to support larger brains, produce more babies and maintain our bodies so we live longer.
Human evolution was not entirely without trade-offs: our digestive tract is smaller and less costly than other apes, which need a large, energetically expensive gut to digest their fibrous, plant-based diets......Our mastery of fire converts otherwise inedible root vegetables—from Trader Joe’s yams to wild Hadza tubers—into veritable starch bombs.
Problematic though it may be in our modern era, our propensity to store fat most likely coevolved with our faster metabolism as a critical energy buffer to survive lean times.
Sharing food is so fundamental to the human experience, the common thread of every barbecue, birthday, bar mitzvah, that we take it for granted, but it is a unique and essential part of our evolutionary inheritance. Other apes do not share.

1.2 The Messy Truth about Weight Loss
Some 600 million, or 13 percent, of the world’s adults were obese in 2014—a figure that had more than doubled around the globe since 1980.....If fad diets, reality television programs and willpower could make a dent in the problem, we would have seen a change by now.
We have shown, for example, that exercise is not the most important thing to focus on when you want to lose weight—although it has numerous other health benefits, including maintaining a healthy weight.....what you eat and how much you eat play a substantially greater role in determining whether you shed kilograms. An adult male of healthy weight and typical height living in the U.S. today requires about 2,500 calories per day to maintain his weight, whereas the average non-obese adult female requires around 2,000 calories. (Men tend to use more calories because, on average, they have larger bodies and greater muscle mass.)
Species as diverse as red deer and gray seals require two to three times more calories, kilogram per kilogram, than primates to maintain their size....The Hadza people in northern Tanzania, a group of hunter-gatherers, and found that the men needed 2,649 calories on average per day. The women, who—like the men—tend to be smaller than counterparts in other regions, needed just 1,877. Another study of the indigenous Yakut people of Siberia found requirements of 3,103 calories for men and 2,299 for women. And members of the Aymara living in the Andean altiplano were found to require 2,653 calories for men and 2,342 calories for women.......On average, Americans consume 500 more calories
each day than they did in the 1970s.
Eventually the researchers determined that the body can extract about four calories of energy per gram from proteins and carbohydrates and nine calories per gram from fat. (These numbers are now known as Atwater factors.).....Raw whole almonds, for example, are harder to digest than Atwater would have predicted, so we get about a third fewer calories from them, whereas we can metabolize all the calories found in almond butter.
So we and others have proved that not all calories are equal—at least for nuts and high-fiber cereals.
Physical activity is responsible for only about one third of total energy expenditure (assuming a stable body weight). The body’s basal metabolism—that is, the energy it needs to maintain itself while at rest—makes up the other two thirds.....Intriguingly, the areas of the body with the greatest energy requirement are the brain and certain internal organs, such as the heart and kidneys—not the skeletal muscle,
Metabolic rate also differs among individuals.....But let us suppose that you have started to lose some weight. Naturally, your metabolic rate and calorie requirements must fall as your body becomes smaller, meaning that weight loss will slow down.....Studies show that metabolic rate drops somewhat more than expected during active weight loss.
the role of hunger has long been to keep us alive. Thus, there is no point in fighting it directly.
Single-meal feeding tests by several labs, including our own, show that meals higher in protein or fiber or those that do not cause a sudden spike in blood sugar (glucose) levels are generally more satisfying and better at suppressing hunger.....calorie consumption in the hours following a breakfast with a so-called high glycemic index (think highly processed breakfast cereals) was 29 percent greater than after a morning meal with a low glycemic index (steel-cut oatmeal or scrambled eggs).
Differences in the hunger-reducing properties of foods, the efficiency with which they are absorbed and the real, though limited, ability of our metabolism to adapt to changes in energy intake make weight management a complex system.....It has been well established that the majority of individuals who are obese secrete proportionately higher levels of insulin, the hormone that helps the body to metabolize glucose. This so-called insulin resistance leads to a host of other metabolic problems,
When we placed such people on a six-month weight-loss program featuring more protein and fiber, fewer carbohydrates and a low glycemic index, we found that they lost more weight than they could on a high-carbohydrate diet with a high glycemic index.
People with low insulin levels, in contrast, did equally well on diets that were higher or lower in the ratio of proteins and carbohydrates, as well as in glycemic index.

1.3 The “True” Human Diet
The “True” Human Diet by Peter Ungar
it’s no surprise that Paleolithic diets remain hugely popular. There are many variants on the general theme, but foods rich in protein and omega-3 fatty acids show up again and again. Grass-fed cow meat and fish are good, and carbohydrates should come from nonstarchy fresh fruits and vegetables. On the other hand, cereal grains, legumes, dairy, potatoes, and highly refined and processed foods are out. The idea is to eat like our Stone Age ancestors—you know, spinach salads with avocado, walnuts, diced turkey, and the like.
From the standpoint of paleoecology, the Paleolithic diet is a myth. Food choice is as much about what’s available to be eaten as it is about what a species evolved to eat.
What was the ancestral human diet? The question itself makes no sense. The Tikiġaġmiut of the north Alaskan coast lived almost entirely on the protein and fat of marine mammals and fish, while the Gwi San in Botswana’s Central Kalahari took something like 70 percent of their calories from carbohydrate-rich, sugary melons and starchy roots.

1.4 Mind over Meal: Weight-Loss Surgery and the Gut-Brain Connection
Connection by Bret Stetka
Teresa had undergone a sleeve gastrectomy.....her weight loss was in all likelihood caused by the drastic change in how her gut speaks to her brain, and vice versa. The procedure had indirectly spurred new neural connections, changing how she thought about and craved food.
Recent science has revealed that appetite, metabolism and weight are regulated through a complex dialogue between bowel and brain—one in which mechanical influences, hormones, bile acids and even the microbes living in our gut all interact with labyrinthine neurocircuitry.
Conversely, the gut can send signals back to the brain, too. In fact, coursing through our abdomen is the enteric nervous system, colloquially known as the second brain. This neural network helps to control food digestion and propulsion through the 30 feet of our gastrointestinal tract. It also communicates directly with the brain through the vagus nerve, which connects the brain with many of our major organs.
Two primary gut-brain pathways regulate appetite. Both systems involve a small, central brain region called the hypothalamus....The first system comes into play during fasting. The stomach secretes the hormone ghrelin, which stimulates a region within the hypothalamus called the arcuate nucleus. This structure then releases neuropeptide Y, a neurotransmitter that, in turn, revs up appetite centers in the cerebral cortex, the outer folds of the brain, driving us to seek out food.
In anticipation of mealtime, our brain sends a signal to the stomach via the vagus nerve, readying it for digestion.....The second gut-brain pathway suppresses our appetite. As we eat, several other hormones, including leptin and insulin, are secreted from fat tissue, the pancreas and the gastrointestinal tract. Separately, these hormones play many roles in digestion and metabolism. Acting together, they signal to another area of the hypothalamus that we are getting full. Our brain tells us to stop eating......Hunger pathways also interact with brain regions such as the amygdala, involved in emotion, and the hippocampus, the brain’s memory center. Hence, our “gut feelings” and “comfort foods” are driven more by moods than mealtimes and nostalgic recollections.......Much like sex, drugs, gambling and other vices, food can cause a surge of dopamine release in the brain’s reward circuitry.
Research has shown that in the days and weeks after bariatric surgery, sugary, fatty and salty foods become less palatable.....The alteration in cravings and taste may be caused by changes in the release and reception of neurotransmitters throughout the gut-brain system.
Palmiter’s work suggests that engagement of the brain stem parabrachial pathway helps us curb our appetite. Because it is this same pathway that becomes unusually active postsurgery, it is probable that the hyperactivation Berthoud discovered is part of the gut-brain’s effort to assess satisfaction postsurgery. As he puts it, “the brain must relearn how to be satisfied with smaller portions.”
There is another player in the complex communications of mind and gut that might explain bariatric surgery’s effects. Experts have implicated the microbiota.
The fact that rodents could lose weight without surgery, simply by receiving microbes from their postoperative fellows, suggests that these microbial populations may be at least partly
Specific gut microbial populations can trigger hormonal and neuronal signaling to the brain such that they influence the development of neural circuits involved in motor control and anxiety. Bäckhed suspects gut flora after bariatric surgery could have a comparable effect on brain regions associated with cravings and appetite.
The neurotransmitter serotonin could play a special role as well. About 90 percent of our body’s serotonin is produced in the gut, and in 2015 researchers at the California Institute of Technology reported that at least some of that production relies on microbes.
In 2015, for example, the U.S. Food and Drug Administration approved a device that stimulates the vagus nerve to quell food cravings.....That approach offers some patients a less invasive alternative to bariatric surgery, but for the moment, vagus nerve stimulators are not as effective as many other obesity therapies.....Acosta Cardenas’s findings support the idea that there are clear subclasses of obesity and that the cause and ideal treatment of obesity is most likely unique to each patient.

2.1 Don’t Diet!
by Charlotte N. Markey
A huge amount of scientific evidence tells us that dieting does not promote lasting weight loss. In fact, many dieters end up gaining back more weight after they quit. Such strategies hardly ever work because they are too extreme and thus almost impossible to maintain over the long term.
My advice as a psychologist and researcher who focuses on weight control: Do not diet.
Making small changes to your eating patterns, ones you can build on slowly over time, is truly the best pathway to lasting weight loss. Although you may have heard this message of moderation before, the evidence is finally too overwhelming to ignore.
Once you give into temptation after restricting yourself, you are more likely to binge.
Vow to avoid pasta, and you will soon find yourself dreaming about spaghetti.
Food preoccupation is an inevitable result of dieting. Psychologists call this phenomenon “ironic processing”—suppressing a thought makes it more salient.
Many studies over the years have shown that people who try to eliminate food groups end up craving those foods intensely.
In fact, treating yourself to indulgences may help you avoid the pitfalls of craving and overeating forbidden foods.
dieters have more difficulty learning new information, solving problems and exerting self-control.
women who restricted their caloric intake and recorded what they ate exhibited elevated cortisol levels, a marker of biological stress.
If you want to improve your body, you must also improve your mind-set. Decades of research show that individuals who are dissatisfied with their bodies are less successful at losing weight. Studies also show that it is possible for anyone to learn to feel good about his or her body.
you need to make gradual, sustainable changes to your diet: for example, drinking less alcohol and juice, substituting diet soda or seltzer for regular soda, and eating dessert on four nights a week instead of seven.
A large body of research supports the idea that making simple, gradual changes to your eating patterns is the best way to promote lasting weight loss....The best tactics, according to the seminal 2006 report, included self-monitoring, such as limiting certain foods, keeping track of portion sizes and calories, planning meals and incorporating exercise into the daily routine.....People who plan their meals are 1.5 times more likely to maintain their weight loss. When combined with better eating habits, however, exercise appears to help people slim down. Incorporating exercise into your life should be a gradual process.
Receiving social support is key to losing weight. Consulting a physician or nutritionist is one way to elicit support and provide greater accountability. Research also demonstrates the role romantic partners play in encouraging weight loss.

2.2 Behaviour: The Additional Key to Weight-Loss
Behaviour: The Additional Key to Weight-Loss by David H. Freedman
A review in 2007 by the American Psychological Association of 31 diet studies found that as many as two thirds of dieters end up two years later weighing more than they did before their diet.....In its strategic plan for funding obesity research, published in 2011, the NIH placed at the top of the list of research opportunities the investigation of basic biological processes related to obesity......The work has also given pharmaceutical companies numerous potential targets for drug development. What the research has not done, unfortunately, is make a dent in solving the national epidemic.
An obesity fix cannot be boiled down to eating certain kinds of food or taking other simple actions. Many factors contribute to the problem. Two stars from me

[Jess · Rating 4 out of 5]

An easy read on the basic sciences and potential results of fad diets or suggested ways of eating and exercise. I like how the book goes through each fad that make these diets not sustainable. The author also takes the stance on wanting insurances and doctors to push park and exercise "prescriptions" versus drugs for mild to moderate depression. She goes through the science behind immersing yourself into trees, parks and Wildlife, and the benefits of doing as such.

[Gerardo Avalos · Rating 4 out of 5]

This is a good, although simplified, review of some myths regarding losing weight. As some of the authors in this compilation of Scientific American papers indicate, the tendency for obesity is the direct effect of our evolution. We evolved to walk long distances and exercise to find enough food -not exercising enough makes fat fast-. The human species was most of the time on the brink of starvation -and thus, we crave fats, sweets, high energy foods-. Gaining weight was a selective advantage under limited resource conditions. Industrialized societies are very new to our species. Superabundant resources and lack of physical activity combine to makes us fat. The key to lose weight and keep it low is to change our behavior and feeding habits. Dieting does not work because it is a shortcut, not a long-term change in habits. Exercising is a very minor component of losing weight. Deciding what to eat, and how much to eat is the key. The scientific information is sound, and the myths fall one by one. I enjoyed the reading.

[Alessandro Piovaccari · Rating 4 out of 5]

Interesting but very simplified summary on new findings about dieting and exercise. Mainly useful as a jump start for further investigation, it is certainly worth reading. I think the first part is certainly the most interesting and new.

[T. Gray · Rating 4 out of 5]

This is a series of articles compiled together. Most are interesting and offer information that i have not heard before. It is a good read on the subject.