The World Health Organization (WHO), the United States Department of Agriculture (USDA), the Food and Agricultural Organization (FAO) and others have been issuing dietary guidelines for decades1-4. The first guidelines were issued in 1916 by the USDA4. The initial goals were to improve public health by preventing deficiencies in nutrients that are essential for good health4. That is, a lack of these nutrients can cause malnutrition and/or non-communicable diseases (NCDs). However, there are other healthy dietary substances like polyphenols and dietary fiber that are not considered to be nutrients. Even though they have many healthy properties, a deficiency of them does not directly result in specific diseases5. Other issues affect the risk of becoming obese. They include highly processed foods, sweetened beverages, alcohol and environmental toxins, as well as the timing of meals and fasting. So, the goals of this two-part article are to describe the problem of obesity, compare and contrast dietary guidelines from different countries, and then to illuminate some of the issues that are not discussed in them. This first part will describe the problem of obesity.
Facts and Statistics
According to Food and Agriculture Organization (FAO) of the UN, hunger in the world has increased from 777 million people in 2015 to 821 million in 2017. In the meantime, 1.9 billion people were overweight, of whom 672 million were obese6. The WHO estimated that 52% of the preventable deaths in 2012 could be attributed to NCDs5,7. A group of scientists and physicians from 195 countries systematically collected data on the diets of adults over 25 years of age to assess the global burden of NCDs caused by poor diet8. They estimated that in 2017, 11 million deaths occurred and 255 million disability-adjusted life years (DALY) were lost primarily due to dietary risk factors. The major risk factors were high intake of sodium, low intake of whole grains and low intake of fruits. The leading causes of diet-related deaths were cardiovascular disease, cancer and type-2 diabetes. Suboptimal diets were responsible for more deaths than any other single cause, including smoking tobacco7. In addition, switching to a primarily plant-based diet from a diet that includes unhealthy animal-based food (red meat and processed meat) is good for your health and for the environment8,9. Note that seaweed and algae like Spirulina are called plant-based foods by many (and are quite nutritious), even though biologists realize that they are actually protists.
In addition, obesity and being overweight are major risk factors for premature deaths and DALY10. In 2010, being obese and/or overweight caused about 3.4 million deaths, 3.9% of years lost and 3.8% of DALYs worldwide. The proportion of men and women who were obese increased from 28.8 to 36.9% in men and from 29.8 to 38.0% in women from 1980 to 201310.
Similarities Shared by Dietary Guidelines in Different Nations
Food-based dietary guidelines (FBDGs) have been published in 90 different countries11. There are common themes in all of them: consume foods in the proper proportions, eat lots of fruits and vegetables as well as limit the intake of sugar, fat and salt11. FBDGs are different than recommended daily allowances (RDAs) that countries publish. RDAs tell how much fat, fatty acids, carbohydrates, cholesterol, protein, amino acids, vitamins and minerals and total Calories (energy) that one should consume. Also, the USDA publishes a Nutrient Database that lists the nutrient levels in hundreds of foods12. The FBDGs tell how much of each food group one should consume to obtain sufficient nutrition, while avoiding obesity.
In the USA, the Food and Nutrition Board, National Academy of Sciences and National Research Council published RDAs for energy, carbohydrates, fat, fatty acids, cholesterol, protein, amino acids, vitamins and minerals13. The RDA is defined as “an estimate of the minimum daily average dietary intake level that meets the nutrient requirements of nearly all (97 to 98 percent) healthy individuals” 13. However, the minimum energy requirements depend on age, sex, weight and amount of physical activity. So, the energy requirements of men who weigh 70 kg is higher (3067 kcal/day) than that of a woman who weighs 57 kg (2403 kcal/day) 14. Note that the units of energy used (kcal) would be readily recognized by physicists, but many nutritionists might prefer Calories (where 1 Calorie = 1000 calories = 1 kcal). So, the Food and Nutrition Board of the IOM included an Acceptable Minimum Distribution Range (AMDR), as well as tolerable upper intake level in their recommendations13,14. The AMDR reflects optimal intake of nutrients, instead of just the minimum requirements14. The daily requirement for energy for a sedentary 19-year old man who weighs 76 kg and is 1.76 m tall is about 37.8 kcal/kg/day. So, the RDA of 0.8 kcal.kg/day would be less than 10% of the energy intake. This is much less than the 35% that is recommended by the AMDR. This led to a widespread misinterpretation of the recommendations. The historically familiar term ‘recommended daily allowance’ was used, but it was defined in a way that many misinterpreted. That is, the word ‘recommended’ implied that the RDA is not a requirement, but just a suggestion. Moreover, the word ‘requirement’ implies that a minimal amount is needed. Also, the term ‘allowance’ might imply to many people that it is the permissible amount and not a minimum amount. The AMDR also concluded that the proportion of total energy (Calories) obtained from protein should be 10-35%. This implies an uncertainty in the amount of fat and carbohydrates that one should consume. Still, there is much evidence to support the idea that the optimal level of protein intake should be higher than the minimum recommended. This is important for maintaining proper muscle mass, strength and function as well as for supporting bone health, maintaining energy balance. It is also important for maintaining proper cardiovascular function and wound healing. So, it was recommended that the term ‘minimal daily requirement’ should replace ‘recommended dietary allowance’. Still, it is the RDA that is recognized by most people and has the greatest influence on dietary practice14.
Almost all FBDGs describe at least four food groups: starchy foods (or grains), fruits, vegetables, and protein foods11. A majority (64%) list dairy products as an additional group, although many include it as part of protein foods. Unfortunately, almost all recommend eating animal-based food and give conflicting recommendations about red meat and dairy. However, the WHO global guidance encourages people to eat more nuts, whole grains and healthy fats. However, many national guidelines don’t do so. Still, most countries’ FBDGs include advice given by the WHO: consume fruits and vegetables (10%), eat at least five portions of fruits and vegetables daily (51%), eat legumes (96%) and whole gains (53%), while limiting free sugars (94%), salt (91%) and fat (94%). Also, almost all FBDGs include an image or picture that is called a food guide. These guides are intended to introduce concepts that are easy to remember: variety, proportionality, adequacy and moderation. Most are pyramids, plates or cultural shapes, such as a house or pagoda. The goal is to attract attention with a new visual cue that reminds people to eat healthy, without providing a specific message11.
One of the things that all dietary guidelines have in common is that they try to use the best scientific evidence available, but they are also influenced by economic, political and sociological factors15. Government organizations may try to put interests of the public first, but the part of the public that controls most of the money has a huge influence on what governments are even allowed to consider to be valid evidence. This is important because the guidelines will affect policies on agriculture and food assistance programs, as well as nutrition in schools, prisons, hospitals and nursing homes. It will also affect the messages that health care professionals and the media will give to the public. In the USA, the USDA and Department of HHS are required to issue new guidelines every five years. Also, the WHO’s International Agency for Research on Cancer (IARC) has studied the effect of dietary factors on the risk of getting cancer. One of its most salient reports was in 2015 when they classified red meat as probably carcinogenic and processed meat as a human carcinogen. Usually, the IARC issues reports within six months of the end of a working group meeting12. However, the report on meat was not published until three years after the working group met12,16. So, it’s important that we try to spread the truth: the best thing that you can do for your health and for the environment is not to eat meat9,17.
Another thing that older dietary guidelines had in common is that they were affected by poor evidence and an incomplete understanding of nutrition. When poor evidence is used to guide public policy decisions it can contribute to the growing burden of preventable, chronic diseases15. For example, the misleading results of animal studies led the USDA to recommend a low-fat diet in the 1970s15. The 1980 guideline had recommendations to “avoid too much fat, saturated fat and cholesterol” 18. In 1985, they recommended that fats be restricted to less than 30% of total caloric intake15. Other governments soon followed. The food industry responded by producing low fat foods. However, to make them more palatable and to increase sales, sugars and starches were added. Potatoes (especially French Fries in fast food restaurants) have been problematic. The Women, Infants and Children (WIC) program is federally funded. It provides vouchers that pregnant women and women with small children can use to buy approved foods. They recommended removing white potatoes from the list of approved foods in 2014, based on a report from the Institute of Medicine (IOM). However, lobbyists from the national Potato Council were able to convince the US government to reverse that decision. The Council argued that potatoes were just as nutritious as other fruits and vegetables15.
Unfortunately, powerful financial and political groups continue to influence guidelines that are being prepared for publication. The current administration in the USA is limiting scientific input into the USDA’s 2020 dietary guidelines19. The committee that will give recommendations for the guidelines has been told not to consider the consumption of red and processed meats nor ultra-processed foods that more people in the USA are eating. The committee is also supposed to avoid exploring the appropriate amounts of sodium that different populations should consume. These are among the most important questions that people face. They are also the questions that much of the food industry does not want us to ask. Also, Congress passed a law in 2015 that prohibited studying the impact of food production on the environment19.
At the same time, governments and international agencies try to find a balance between making their reports simple enough to be understood by non-scientists and not being accurate. Sometimes one loses accuracy in oversimplification. For example, there has been a common, but inaccurate theme in articles on obesity. That is, we have been thought to be like machines. This type of reductionist thinking leads one to believe that to maintain our body weight, the number of Calories that we consume must equal the Calories that we burn up. The phrases “calories in and calories out” and “energy balance” have been repeated through the years and up to 201920-22. This is wrong. We are not machines. Our body weight depends on much more than simply our energy balance. So, the goal of governments should be to emphasize the importance of eating healthier at the proper time of day, avoiding environmental toxins (obesogens) AND being physically active. This message may help save the lives of countless millions of people. However, if one decides to make the effort to learn more, this oversimplified message can be augmented.
Not All Calories Are the Same and Lifestyle is Important
A major cause of the increase in obesity is the change in the types and quality of foods that are eaten23. Poor sleeping habits are also problematic. The quality of the diet is affected by the amount and types of carbohydrates that are eaten, as well as the amount of dietary fiber and the types of fat and protein. Watching television is also a factor. It can lead to mindless eating. Moreover, food marketing and commercials can lead people (especially children) to eat foods that are high in sugar and salt, as well as saturated and trans fats. Overall food quality and diet can also affect health. That is, obese people can reduce their risk for disease by eating a healthy diet, while some lean people can develop metabolic dysfunction and disease by consuming a poor diet23.
Not all Calories have equal impact on obesity and health23. Saturated and trans fats are more obesogenic than cis, omega-3 and polyunsaturated fats. Some foods that people are taught to like can lead to hedonistic eating. Hedonistic foods excite the reward centers of the brain23. If young children are taught that eating candy and drinking sweetened beverages are rewards for “being good”, such foods can become hedonistic throughout life. In contrast, when people stop drinking sweetened beverages and candy, their tastes can change. Such foods and beverages no longer taste good. Social conditioning and training can also help. Children studying martial arts like Tae-Kwon Do are taught no to eat candy.
Diet quality also affects the microbiome23. Not all carbohydrates are the same. Simple sugars lead to obesity and an unhealthy gut microbiome. Complex carbohydrates like inulin (a soluble dietary fiber and prebiotic) can help build a healthier gut microbiome as can yogurt (a probiotic). In contrast, milk and cheese contain saturated fats that can lead to an unhealthy gut microbiome23. When healthy, the gut microbiome can help prevent cancer.
Diet quality can also affect one’s ability to keep weight off once it is lost23. In a prospective clinical trial, it was found that one’s energy expenditure decreases after losing weight23,24. That is, we reach a “set point” in our weight. After losing weight, one’s metabolic rate decreases during the period of weight loss maintenance23. This can cause people to feel cold and tired and even start gaining back the weight they lost. However, eating a low-fat diet caused more of a decrease in metabolic rate than either a high-fat diet or a diet of carbohydrates that have a low glycemic index23. This suggests that a diet higher in healthy fat and lower in simple carbohydrates is preferred.
Diets are not simply a choice made solely by each person. Education, socio-economic status, culture, health status, knowledge about nutrition, cooking skills, watching TV and sleep can all affect one’s diet23. The foods available at the work place and in neighborhood supermarkets are also important. So, government policies that support and incentivize the mass production of beef and tolerate pollution can cause much damage. The changing ideas of what makes a person attractive can also influence attitudes about obesity. In the 1950s male role models were tall and overweight with large arm muscles. Now they tend to have little body fat and well-developed abdominal muscles (a six pack) 23.
To make real, beneficial changes, it’s important to address the multifactorial nature of obesity23. We can look at how government policies reduced the number of deaths per vehicle mile caused by the automotive industry in the USA between 1925 and 1995 by 90%. It was not done primarily by focusing on individual choices (like drive safely). Instead the government used a multicomponent strategy. It addressed not just the driver, but also the car, the road and the culture. Similarly, governments should do more than just try to educate individuals and put warning labels on some foods and sweetened beverages. Instead, they should focus on the quality of foods and diet. This should include media campaigns, comprehensive programs for schools and workplaces, economic incentives, stop price supports for producing meat (especially beef), subsidize the production of healthy foods, improve quality standards for food additives, limit the marketing of candy, fast foods, sweetened beverages and cereals to children and improve long-term agricultural policies to facilitate production, transportation and marketing of healthier foods23.
So, a new model of obesity has been described25. Consuming processed foods and simple carbohydrates with a high glycemic load promotes fat deposition in adipose tissue, increases appetite and lowers the expenditure of energy. This is due in part to hormonal changes. Insulin stimulates the uptake of glucose into tissues while promoting the deposition of fat and glycogen, which can lead to obesity. Consuming large amounts of refined starchy foods and sugar increases the concentration of insulin in the blood. The Carbohydrate-Insulin Model teaches that overeating is a consequence of obesity (or adiposity) and not a cause. People can get caught in a vicious circle. Overconsumption of simple carbohydrates can lead to obesity, which leads to overeating. From this perspective, restricting caloric intake treats the symptoms and not the cause of obesity. So, it is almost always destined to fail. After completing a diet, often one’s body weight spontaneously returns to or near the baseline or “set point” 25. We are not machines.
The role of adipose tissue (fatty tissue) is also not characteristic of a machine. It does much more than just store energy as fat (triglycerides) 26. It’s also an endocrine organ that secretes the peptide hormones leptin and adiponectin. These hormones affect appetite, lipid and glucose metabolism, energy balance, the amount of systemic inflammation and tissue repair. People who don’t have either the genes that code for leptin or the leptin receptor are very obese, hyperglycemic and extremely resistant to the effects of insulin in controlling blood sugar (glucose) 26. Moreover, disrupting our daily circadian rhythms seriously affects metabolism and homeostasis27. The central clock (or pacemaker) in the brain oscillates and synchronizes the network of peripheral clocks that are in all tissues and cells. Circadian clocks are affected by not just the day/night cycle, but also energy intake and the timing of meals. Chronic disruption of the circadian rhythm can lead to metabolic syndrome, cardiovascular diseases and type-2 diabetes27.
Having a regular pattern of eating with more in the morning, no more than three times a day and regular fasting can reduce inflammation, improve circadian rhythmicity and the gut microbiome as well as increased stress resistance28. In one study, eating only one or two meals a day was associated with a lower body mass index (BMI). The longer the overnight fast, the lower the BMI. It’s also better to consume more Calories earlier in the day28. However, this may not be desirable in societies where this is not popular. Since eating is usually a social event, it can be important to follow the norms of society to be accepted and to avoid loneliness, which is unhealthy.
In conclusion, government agencies have been issuing dietary guidelines for decades. Food-based dietary guidelines (FBDGs) have been published in 90 different countries11. There are common themes in all of them: consume foods in the proper proportions, eat lots of fruits and vegetables as well as limit the intake of sugar, fat and salt11. FBDGs are different than recommended daily allowances (RDAs) that countries publish. RDAs tell how much fat, fatty acids, carbohydrates, cholesterol, protein, amino acids, vitamins and minerals and total Calories (energy) that one should consume. Also, the USDA publishes a Nutrient Database that lists the nutrient levels in hundreds of foods12. The FBDGs tell how much of each food group one should consume to obtain sufficient nutrition, while avoiding obesity. Still, hunger in the world continues to grow, as do the number people are overweight. Suboptimal diets were responsible for more deaths than any other single cause, including smoking tobacco7. In addition, switching to a primarily plant-based diet from a diet that includes unhealthy animal-based food (red meat and processed meat) is good for your health and for the environment.
Next month, I will describe historical differences in dietary guidelines and then describe differences between current guidelines from different countries. Finally, I will describe important issues that are not in current guidelines, despite their importance. Not all calories are the same. Lifestyle factors (timing of meals, amount of sleep, exposure to toxins in the environment) are important to. These will be discussed.
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