Our Changing Eating Patterns

The U.S. Department of Agriculture recently published information on the sources of our daily caloric intake between 1970 and 2008, a time period in which our daily caloric consumption increased by 23.2% from 2,169 cals to 2,672 cals, and rates of overweight and obesity have risen sharply. An interactive graphic was created from the data that allows users to scroll along a time-line to see how the amount of daily calories in each food category has changed over time. The following are the percentage changes in calories coming from each food category:

meat, eggs, and nuts: +4.1%
fruit:                         +22.9%
added fat:                 +56.3%
dairy:                          -3.7%
grains:                      +44.7%
vegetables                   -2.4%
added sugar              +14.2%

Some Observations on the Data

In Terms of Absolute Calories

• The biggest contributors by far to our increased daily caloric intake are added fat (231 cals) and grains (193 cals).
• Much more modest contributors to our increased daily caloric intake are added sugar (57 cals), meat/eggs/nuts (19 cals), and fruit (16 calories).
• Our daily consumption of dairy actually decreased by 10 calories and of vegetables by 3 calories.

In Terms of Percentage of Daily Calories

• The only foods that increased as percentages of our diet from 1970 to 2008 are added fats (from 18.9% to 24.0% of daily calories) and grains (from 19.9 % to 23.4% of daily calories).
• Caloric consumption from fruit was steady at 3.2 % of calories.
• All other foods declined as percentages of our daily calories including meat/nuts/eggs (from 21.3% to 18.0% of daily calories), dairy (from 12.3% to 9.6% of daily calories), added sugar (from 18.5% to 17.2% of daily calories), and vegetables (from 5.8% to 4.6% of daily calories).

Bottom Line
The greatest contributors to our increase in caloric consumption are grains and added fat. While we have increased our intake of all other foods except vegetables, grains and fat together account for 84% of our increase in caloric consumption and should therefore be the prime focus of cutting back calories. This makes it clear that the low-fat and low-carb diets are both missing something because the intake of both must be reduced. Any diet that emphasizes what you eat rather than how much you eat is bound to fail. Overweight and obese people who seek to attain a healthy body weight must face the reality that total intake must be lessened. Focusing on eating both fewer grain-based foods and fewer added fats is a good start.

Fatty Liver Disease: Another Reason to Avoid Obesity

An article in the January 2011 issue of the Harvard Health Letter reveals that the epidemic of obesity has increased the occurrence of fatty liver disease. Previously, most cases of fatty liver disease were related to excess alcohol consumption, but now, many cases are related to excess body fat, which can lead to Type II diabetes. Fatty liver disease affects 70-90% of those who are obese and/or have diabetes.

Abdominal obesity can lead to metabolic syndrome (elevated blood pressure and levels of triglycerides and blood sugar, and low HDL (good cholesterol). Overfilled fat cells become resistant to insulin (which lowers blood sugar by storing it in the cells) resulting in excess fatty acids in the blood. Fat then accumulates in liver cells, which can lead to inflammation and liver tissue damage.  This can in turn bring about liver fibrosis (buildup of fibrous tissue) or cirrhosis (buildup of scar tissue). Cirrhosis increases the risk of liver cancer.

Fatty liver disease increases the risk of heart attack and stroke because a fatty liver produces inflammatory factors that can promote the deposition of plaque in the arteries, leading to arterial narrowing.

The only effective treatment for fatty liver disease is to lose weight.

Bottom Line
If you want to avoid or reverse fatty liver disease, avoid gaining unnecessary body fat or lose existing excess body fat through a program of good nutrition and exercise. Both caloric restriction and exercise are essential parts of any weight-loss program.

New Insights into Obesity

The December 2010 issue of the Nutrition Action Health Letter, published by the Center for Science in the Public Interest, featured an interview with Eric Ravussin, head of the Nutrition Obesity Research Center of the highly regarded Pennington Biomedical Research Center in Baton Rouge, LA. The discussion centered on new clues as to why we gain weight, and revealed the following:

• Leptin, a hormone discovered in 1994, is produced by fat cells and  tells the brain when the cells are full.
• When people diet and lose weight, leptin levels drop sharply, causing food cravings and weight regain.
• Loss of 10-20% of body weight slows the metabolism and rate of caloric burn.
• Injecting leptin can bring the metabolism back up.
• However, most overweight people are resistant to leptin, just as Type II diabetics are resistant to insulin.
• Using drugs to shut down hunger mechanisms doesn’t work well because the human body has developed several redundant systems to stimulate eating as protection against starvation.
• People have natural ranges of body fat depending on their genes that control energy intake and expenditure.
• Nutrition in the womb and infancy can affect propensity for overweight and obesity by switching different genes on and off.
• Brown adipose tissue, which burns calories to produce body heat, previously thought to exist only in infants, was recently discovered in adults.
• By maintaining homes at a steady comfortable temperature throughout the year, we don’t burn calories via brown fat to keep warm in winter, and we miss the appetite-suppressing effect of heat in the summer.
• A common cold virus (adenovirus-36) makes experimental animals gain a lot of weight. Antibodies to this virus, an indication of exposure, are much more common in obese than in normal-weight people.
• Gut bacteria can be a factor. Transplanting feces from a fat animal to a lean one results in weight gain for the latter, while transplanting from the lean to the fat animal makes the fatter one leaner. Similar transplants in humans have reduced insulin-resistance of people with metabolic syndrome, a set of symptoms indicative of heart-disease risk characterized by excess fat around the waist, low HDL, and elevated blood pressure, blood triglycerides, and fasting blood glucose.

Ravussin feels that we should tax soft drinks and other unhealthy foods while subsidizing healthy foods, create areas where kids can safely play, and make physical education mandatory so that everyone, not only the athletically-gifted, engages in physical activity,

Are There Hidden Causes of the Overweight Epidemic?

In the December 20, 2010 issue of Newsweek magazine, Sharon Begley, the magazine’s science columnist, wrote that there are some little-known factors that may contribute to the continued increase in the prevalence of overweight and obesity. Her main argument is that it must be more than a matter of exercising more and eating better because, among animals that have contact with human beings, such as pets, lab animals and rodent pests, 23 of the 24 species studied since 1940 have shown significant increases in the percentages of overweight and obese animals, a statistic that could have occurred by chance only once in 8 million. Yet changes in diet and exercise don’t appear to be the reason, as these factors haven’t changed much for these animals over the years.

Begley cites some possible reasons other than diet and exercise for the weight gain of animals and, by extension, us:

• The type of bacteria in our gut - more efficient bacteria wring more calories out of our food than do less efficient bacteria. In this case, efficiency is not our friend.
• Lack of sleep, which increases the appetite-stimulating hormone ghrelin, and decreases the hormone leptin that suppresses our appetite when we’ve eaten enough.
• Environmental chemicals such as BPA that stimulate fat-cell production.
• Home heating, which lessens the need for the body’s calorie-consuming heat production.
• Home air conditioning, which lessens the appetite-suppressing effect of environmental heat.
• Infection with adenovirus-36, which causes obesity in  lab animals and is correlated with obesity in humans.

In addition, I feel that there may be another contributor to obesity:

• The lack of internal parasites due to modern sanitary practices. If parasites eat some of our food, less of it can be packed on as fat. If they partake of our bodies, then energy must be consumed for repair. This assumes the kind of parasites that are relatively harmless other than consuming some of our food or body tissue.

Bottom Line
There is no doubt that our health benefits from exercising regularly and eating a healthy diet without excess calories. However, we must continue to look for other contributing factors in order to effectively deal with and counteract the continued rise in overweight and obesity that threatens to undermine the gains we’ve made in improving our health and increasing our lifespan.

Estimating the Caloric Cost of Running or Walking

A recently published article by Loftin et al. in the Journal of Strength and Conditioning Research (vol. 24, no. 10, pp. 2794-2798, 2010) measured the caloric consumption per mile of 19 normal-weight walkers, 11 overweight walkers, and 20 marathon runners. The subjects were about evenly divided among males and females.

Results

• Caloric consumption was more related to lean body mass than to total body mass
• Men burned more calories per mile than women
• Men and women did not differ in calories consumed per mile per unit body mass
• In terms of calories per mile per unit body mass, marathon runners burned significantly more than normal-weight walkers who burned significantly more than overweight walkers

The following equation was developed from the experimental data to predict an individual’s caloric consumption per mile:

Men weighed in kilograms:

Calories per mile = (0.789 x kg body mass) + 43.5

Men weighed in pounds:
Calories per mile = (0.3586 x lb body mass) + 43.5

Women weighed in kilograms:

Calories per mile = (0.789 x kg body mass) + 35.8

Women weighed in pounds:
Calories per mile = (0.3586 x lb body mass) + 35.8

Bottom Line

The equation can be useful for those interested in estimating the caloric cost of their walking or running workout.