Over the last century, we’ve seen experts promote vastly different types of diets for health. The USDA has issued dietary guidelines for over 100 years. From the 1900s to 1940s, they established food groups based on protein, carbohydrates, and fats, and recommended a diet primarily based on carbohydrates. From the 1940s to 1970s, many essential vitamins were discovered, which led to establishing Recommended Daily Allowance (RDA) values and a focus on meeting those values. From the 1970s to 1990s, there was a large emphasis on avoiding saturated fats, cholesterol, and salt.  The most recent dietary guidelines, published in 2015, recommends a diet high in vegetables, fruit, whole grains, low- or nonfat dairy, seafood, legumes, and nuts; and low in red or processed meats, low sugar-sweetened food and drinks and refined grains, and moderate consumption of alcohol (in adults). Since many changes have taken place over a relatively short time, it can be difficult to heed advice that reveals the long process of understanding nutritional science. And because nutrition is personal, there are far-reaching opinions of what one should or should not eat.

Half of the American adult population has a preventable chronic disease, and over two-thirds of American adults are overweight or obese. Given this scenario, of course our altruistic friends and family, our neighbors, our mailwoman, and internet experts will want to share their own experience of what diet worked for them. In the same time that the USDA has been issuing dietary guidelines, popular opinion for how to lose weight has ranged anywhere from smoking cigarettes instead of eating sweets or drinking only a shake for each meal to swallowing tapeworms. Obviously, just because it works for one person, doesn’t mean it will work for another, or that it’s even safe to begin with. Now in the nutritional ethos, we are told to eat mostly proteins and vegetables, OR avoid all animal products, OR just drink bone broth, OR avoid all grains, OR be gluten free, and on and on. Although any of those options sound easier and preferable to swallowing parasites, all the varying and adamant advice can be confusing, or worse, discouraging from even trying at all.

Let’s work our way out of some of the confusion by clarifying or debunking some mainstream myths.

Myth: Weight loss absolutely occurs when energy expenditure exceeds energy intake. This is mostly true when what goes in actually comes out. However, that doesn’t always happen and not all calories are created equal. When we eat mostly vegetables with plenty of fiber, calories almost don’t matter for maintaining weight. The China Study by T. Colin Campbell showed that people in rural China ate 20% more daily calories than American counterparts, but were able to maintain healthy weights and health measures because most of the diet was composed of plants. (For losing weight, it may be helpful to limit portion sizes.) There were no processed foods in the diets studied. Many processed foods have preservatives that slow the function of the liver, or are difficult to process and are stored instead. This may help explain the phenomenon of being malnourished and overweight. Even when consumption of calories is limited, food quality influences metabolism and nourishment.

The idea that weight loss and gain is only determined by calorie consumption and expenditure is damaging to behavior for a number of reasons. One reason that we hinted at already is that it allows people to eat food regardless of food quality or category as long as it is below their calorie expenditure. It can lead to the belief that you can eat anything you want all the time and just exercise excessively. Or you may start to deprive yourself of food, leading to a variety of issues including a dysfunctional relationship with food, irregular eating patterns, or eating disorders. A woman I used to see years ago who was trying to lose weight wouldn’t eat breakfast and lunch partly because of this belief, and partly because she could use work as an excuse to not eat. By the time she got home, she would indulge for dinner with whatever food or snacks were available all through the night, and she kept gaining weight. Adding food for breakfast and lunch was actually important for her to start losing weight.

Therefore, what matters more than calories is eating many servings of high quality, well-prepared vegetables daily. However, this doesn’t mean that portion control is not a factor. Limiting the size of your plate or bowl and eating until satisfied or between 60% to 80% full contributes to retraining the central nervous system and visceral organs. Also, eating at regular times will stimulate metabolism and help with digestion.

Myth: There is one healthy way to eat. This idea makes it difficult to write dietary guidelines that are supposed to be general rules for everyone. Yet, having dietary guidelines sort of promotes the idea that there is only one healthy way to eat. In fact, in the Scientific Report of the 2015 Dietary Guidelines Advisory Committee, many, but not all studies showed beneficial health outcomes from consuming whole grains, dairy, seafood, and legumes, even high amounts of these foods made it into the 2015 dietary guidelines. Not surprisingly, different people have different capacities to tolerate or process certain foods. More and more studies are starting to distinguish optimal diets on an individual basis. A recent study showed that blood sugar levels in 800 prediabetic people could significantly alter even when people ate identical meals. Some could eat bread with no sugar changes, while others blood sugar would spike after eating bread. Another person’s blood sugar could spike after eating a tomato. The results varied dramatically. Also, studies have shown that certain genes favor improved glycemic control. We can also expect to understand personalized nutrition more as more research comes out about differences in the microbiome.

Eating on an individual basis can get tricky. Our first inclination may be to try out a myriad of diet assessment and treatment protocols. Some of these are the GAPS diet, FODMAPS diet, Blood Type Diet, Genotype Diet, Ayurvedic dosha diets or Chinese 5-elements diets, etc. These can be useful tools when applied appropriately, but they can be hindrances to eating timely healthy meals with others. They can be time consuming to prep, confusing to follow, and damaging to our appreciation of food. Through these methods, if utilized inappropriately, we may also develop an unhealthy fixation with food and its effects. Also, if everyone in your family assumes they do best on a different diet, does it make sense to cook 4 or 5 meals? Heck no! It’s necessary to be aware of how healthy eating based on the individual can be taken to an unhealthy extreme, but it doesn’t have to be this way. If the general assumption is that everyone tolerates certain foods differently, people will have more freedom and opportunities to eat healthfully. We would be more apt to be aware and know how we react to certain things at an early age. Assuming that everyone responds to foods differently would prioritize having a healthy variety of foods at each meal. Shifting popular opinion to “there are many healthy ways to eat” will produce a healthier population.

Myth: I’m the kind of person that tolerates processed foods and desserts. Despite the variety of ways to be healthy, there are some hard facts about what all humans should or should not eat. We should eat vegetables and fruits. Every study ever shows that people are healthier with high amounts of daily vegetable intake. Most studies show people are healthier with high amounts of fruit intake, though not all. On the other end of the spectrum, high sugar and refined grains intake is associated with increased risk for cardiovascular disease, diabetes, cancer, and poor health outcomes. 47% of added sugar is consumed from beverages. High sugar/high fat diets have been shown to lead to high insulin and high blood pressure. Yet, low fat diets are also not effective for weight loss. (This is another example of the downfalls of having a microscopic focus when it comes to food. Instead of looking at the larger picture of what foods are consumed, we whittle down foods to only calories or fat, which distract us from what it really means to eat healthfully.) Increased salt consumption, which is also associated with poor cardiovascular outcomes, primarily comes from eating mixed processed foods, burgers and sandwiches. Processed foods also contain a number of preservatives that are still not well studied. Though many of these chemicals are approved by the FDA, many cannot tolerate them. And as mentioned earlier, these chemicals are often not metabolized fully, and stored in fat cells. Furthermore, there continues to be more evidence of endocrine disrupting chemicals in food. These foods alter the hypothalamic-pituitary axis (which we discussed in the Physiology of Obesity). Ultimately, these chemicals change the rate of metabolism over time.

What works?

If you came to my Inflammation lecture, you’ll know that a good place to start is eating a whole foods, plant-based diet. With the assumption that there is not just one healthy way to eat, eat mostly vegetables and fruits; and if you tolerate them, some grains, legumes, dairy, seafood, nuts, seeds, and meat; less alcohol and processed foods; and avoid refined sugar and sweetened beverages. This is not that different from the current dietary guidelines (except I recommend more than 2-3 cups of vegetables per day) Most people will benefit from these general suggestions. Studies have determined that less than 10-30% of all Americans (depending on age group and sex) eat enough vegetables per day (only 2-3 cups) according to the 2015 Dietary guideline suggestions. These numbers have declined since 2001. 80% of Americans also don’t meet the requirement for fruit consumption (1.5-2.5 cups). For those who need more specific guidelines, there are a couple diets that have been studied to help with weight loss. (Keep in mind that many diet protocols have not been studied.) The Mediterranean diet has shown to decrease weight, blood pressure, and cardiovascular risk. Another diet associated with decreased risks of chronic disease and increased longevity arising from a culture is the Okinawa diet. The common theme is to eat a plant-based diet creating a culture of eating with people in your community and celebrating food.

Other suggestions: Eat at regular times, eating dinner no later than 2 hours before bedtime. Eat until you are 80% full. If you’re trying to lose weight, eat until just satisfied. Eat with people. Eating with people also shows improved cardiovascular risk.

References

• Campbell TC, Schurman JC, Campbell TM. The China Study. BenBella Books, 2004.
• Frazão, Elizabeth. America’s Eating Habits: Changes and Consequences. Agriculture Information Bulletin No. (AIB-750) 494 pp, May 1999. http://www.ers.usda.gov/media/91022/aib750b_1_.pdf accessed 1/6/15
• Gower, B. Obesity Week 2015; Los Angeles, CA. Abstract T-OR-2108, presented November 3, 2015.
• Khoury M, Manihiot C, Gibson D, et al. Evaluating the associations between buying lunch at school, eating at restaurants, and eating together as a family and cardiometabolic risk in adolescents. Canadian Cardiovascular Congress; October 24, 2015–October 27, 2015
• Tobias DK, et al. Effect of low-fat diet interventions versus other diet interventions on long-term weight change in adults: a systematic review and meta-analysis. Lancet Diabetes Endocrinol 2015. Published online October 30, 2015. http://www.thelancet.com/pdfs/journals/landia/PIIS2213-8587%2815%2900367-8.pdf Accessed 1/8/15
• USDA. Scientific Report of the 2015 Dietary Guidelines Advisory Committee: Advisory Report to the Secretary of Health and Human Services and the Secretary of Agriculture. Feb 2015. http://health.gov/dietaryguidelines/2015-scientific-report/PDFs/Scientific-Report-of-the-2015-Dietary-Guidelines-Advisory-Committee.pdf accessed 1/6/15
• Willcox DC, et al. The Okinawan diet: health implications of a low-calorie, nutrient-dense, antioxidant-rich dietary pattern low in glycemic load. J Am Coll Nutr. 2009 Aug;28 Suppl:500S-516S.
• Zeevi D, et al. Personalized Nutrition by Prediction of Glycemic Responses. Cell. 2015 Nov 19;163(5):1079-94.