Eating Right: What the Science Says
Diet experts separate fact from fiction on ketogenic, Paleo and plant-based strategies (plus many more).
Technology makes so much nutrition information available at the touch of a button that people get muddled about what, when and how much to eat. Case in point: A Google search of “intermittent fasting” yields a mix of criticism and rave reviews. Numerous varieties of intermittent fasting also pop up, adding to the confusion.
How do you give your clients practical, evidence-based suggestions amid all these mixed signals? Below, experts weigh in with scientifically grounded advice on some
of your clients’ most pressing nutrition questions.
What Is a Ketogenic Diet?
Overview: Used in the 1920s as a treatment for epilepsy, the ketogenic diet has since been considered as a potential treatment for diabetes, cancer and cardiovascular disease. In the 1970s, the Atkins Diet® popularized a ketogenic strategy for weight loss (Paoli et al. 2013).
Experts say: “A ketogenic diet is very low in carbs, relatively low in protein and very high in fat,” says Brian St. Pierre, MS, RD, CSCS,
director of performance nutrition at Precision Nutrition. “This leads to relatively low levels of blood glucose, which our brains (and other organs) need to function, so our liver makes ketones as an alternative energy source.”
Apply it with clients: “Some folks find this style of eating helps them manage their hunger and cravings, lose body fat, and look and feel their best,” says St. Pierre. “Others find it very difficult to follow, or they report brain fog and low energy. Like most dietary approaches, it will work for some, but not for all.” Encourage clients to be realistic about nutritional changes, and emphasize strategies they can maintain over the long term.
Are Cholesterol and Saturated Fat “Bad”? Is Butter Really “Back”?
Overview: Butter is once again in the nutrition spotlight, and now people aren’t just putting it in their baked goods (butter coffee, anyone?). Recent research has re-examined the relationships among dietary cholesterol, saturated fat and heart health. A controversial 2015 review in the British Medical Journal found no correlation between saturated-fat intake and cardiovascular disease (De Souza et al. 2015). However, replacing saturated fats with unsaturated fats is linked to a reduction in cardiovascular disease risk (Siri-Tarino et al. 2010).
Experts say: “For most people, dietary cholesterol doesn’t have a large impact on blood cholesterol,” says Mardi Parelman, PhD, assistant professor of nutritional sciences at Miramar College in San Diego. The same can’t be said of saturated fat. “Eating a lot of saturated fat does raise LDL, or ‘bad’ cholesterol,” says Natalie Digate Muth, MD, MPH, RDN, LDN, FACPP. “It’s best to replace saturated fat with polyunsaturated fat—not processed carbs.”
Apply it with clients: “Ask clients to consume more monounsaturated fats [from foods] like olives, avocados, almonds and cashews, and more omega-3 polyunsaturated fats [from] fatty fish, flaxseed or walnuts. Look to fruits and vegetables, whole grains and lean proteins to replace calories from saturated fat,” Parelman says.
How Do I Fuel My Workouts With a Plant-Based Diet?
Overview: A recent study comparing vegetarian and omnivorous endurance athletes found no difference in force production, but VO2max levels were higher among female vegetarian athletes than among their meat-eating counterparts (Lynch, Wharton & Johnson 2016). However, vegetarian and vegan athletes often have lower levels of iron and muscle creatine, which can hurt performance (Barr & Rideout 2004).
Experts say: “Fueling with a plant-based diet is no different than [following] any other diet when it comes to macronutrients,” says Christopher Heslin, MS, CNS, supervising health educator for the Kaiser Permanente Positive Choice Integrative Wellness Center. “Preworkout meals should consist of moderate-glycemic-index carbs with protein and be lower in fat and fiber for gastric comfort. Postworkout meals should include large amounts of colorful produce and omega-3s to fight inflammation, along with plant-based proteins to promote recovery.”
Apply it with clients: Heslin suggests soy, textured vegetable proteins or legumes to provide postworkout protein. Muth encourages eating plant-based iron sources, such as beans, lentils, spinach, tomatoes and broccoli, paired with foods high in vitamin C to enhance absorption.
I’ve Heard I Can Get Really Lean on the Paleo Diet®. Should I Try It?
Overview: The “Paleo” Diet suggests mimicking the meals of our cave-dwelling ancestors, focusing on foods they presumably ate and avoiding the rest. Hence, Paleo
typically includes unprocessed meat, fish, eggs, vegetables, fruit, nuts and seeds, while it prohibits grains, dairy, sugar, legumes, potatoes and processed foods.
Experts say: “While the evolutionary arguments behind the Paleo Diet don’t hold up, it likely gets more right than it gets wrong. The emphasis on whole foods, lean proteins, vegetables, fruits, nuts, seeds and other healthy fats is a massive improvement over the average Western diet,” says St. Pierre. “However,” he cautions, “the evidence for excluding dairy, legumes and grains isn’t strong. Most of us can improve the way we look, feel and perform without completely eliminating these foods.”
Apply it with clients: “Strictly following a list of ‘good’ and ‘bad’ or ‘allowed’ and ‘not allowed’ foods tends to be problematic,” says St. Pierre. “It makes us feel more confident and (falsely) sure of ourselves in the short term. But it’s less effective over the long term because it ultimately decreases our consistency.” Encourage clients to focus on what they can eat—whole, diverse and minimally processed foods—rather than restricting certain food groups.
How Many Calories Should I Eat Each Day?
Overview: Clients often assume the fewer calories they eat, the better. This can be problematic because calorie restriction raises cortisol levels, which can lead to weight gain over time (Tomiyama et al. 2010).
Experts say: “Strict calorie counting is tedious, inexact and unsustainable,” says St. Pierre. “It takes handbooks, websites, databases and math—just to plan lunch.” He cautions that calorie counts are often wrong by up to 25%, offering clients less precision than they might assume (Livesey 2001). “While calories do count,” he says, “it’s clear that counting them won’t help most people over the long term.”
Apply it with clients: Precision Nutrition uses a hand-based model to determine portion sizes (see “A Handy Alternative to Counting Calories” by St. Pierre and John Berardi, PhD, in the April 2016 issue of IDEA Fitness Journal). “Hands are scaled to the individual,” says St. Pierre. “The bigger you are, the bigger your hands tend to be. Since larger people typically need more food, it works itself out.”
Do I Really Have to Eat Breakfast?
Overview: The National Weight Control Registry says regular breakfast consumption is common among those who have lost at least 10% of their body weight and kept it off for over a year (Wing & Phelan 2005). However, an American Journal of Clinical Nutrition review suggests the quality of studies on this topic has been poor and the role of breakfast in weight management has been overstated (Brown, Bohan Brown & Allison 2013).
Experts say: “This is an age-old question without a clear-cut answer,” says Muth. “If you’ve never eaten breakfast and you’re able to get all your recommended nutrient needs at other times (including 5–9 servings of fruits and vegetables) without overeating, then it may not be needed.” However, she cautions, few people actually fit that category. “If you’re working to meet energy needs (both literally from calories and to get through the day with sufficient ‘umpf’), then breakfast is important,” she says.
Apply it with clients: Ask clients who skip breakfast to take inventory of their eating habits. Do they feel energized throughout the day? Are they insatiable in the evening? Encourage experimentation with breakfast to see how energy, mood and cravings respond.
What’s the Best Diet for Heart Health? Will It Help Me Lose Weight?
Overview: A review in JAMA Internal Medicine says the Mediterranean diet stands above the rest in the prevention of cardiovascular disease (Widmer et al. 2015). The Mediterranean diet is high in fish, olive oil, nuts, vegetables, fruits, legumes and whole grains and is moderate in alcohol consumption.
Experts say: “The DASH [Dietary Approaches to Stop Hypertension] and Mediterranean diets have the most evidence to support lowering cardiovascular disease risk,” says Heslin. “Any diet that restricts calories will lead to weight loss. The question is whether or not it’s sustainable. The Mediterranean diet focuses on eating more plant-derived fats, colorful produce and lean proteins,” he says. “It’s nothing too crazy or fancy—just commonsense nutrition.”
Apply it with clients: Encourage clients to focus on fruits, vegetables, whole grains, healthy fats and lean proteins, all of which are common to the DASH and Mediterranean diets.
Should I Try Intermittent Fasting?
Overview: The research on intermittent fasting is relatively new and inconclusive. A recent study published in the Journal of American Medicine found no difference in weight loss between alternate-day fasting and daily caloric restriction (Trepanowski et al. 2017).
Experts say: “Intermittent fasting is a hot trend, with the science lagging on whether it is more effective than any other approach to losing weight,” says Muth. “The research that does exist shows that it is an effective method to help support weight loss.”
Apply it with clients: Encourage clients to start with the “big rocks” of weight loss (i.e., consuming adequate fruits and vegetables, increasing daily movement) before advising more extreme measures. For those interested in fasting, suggest a moderate start, such as 1–2 fasting days a week at 25% of daily caloric needs.
As nutrition information continues to evolve, so too will clients’ food-related questions. While the vilified macronutrient or hot diet of the week may change, the benefits of whole and minimally processed foods will not.
Offer your clients evidence-based advice, but ask them, “How does this food fit into the context of your life? What have you noticed when eating or omitting it in the past? Would this be a sustainable change for you?” In this way, you’ll support client autonomy and empower people to develop healthier eating habits for life.
Barr, S.I., & Rideout, C.A. 2004. Nutritional considerations for vegetarian athletes. Nutrition, 20 (7-8), 696–703.
Brown, A.W., Bohan Brown, M.M., & Allison, D.B. 2013. Belief beyond the evidence: Using the proposed effect of breakfast on obesity to show 2 practices that distort scientific evidence. American Journal of Clinical Nutrition, 98 (5), 1298–1308.
De Souza, R.J., et al. 2015. Intake of saturated and trans unsaturated fatty acids and risk of all-cause mortality, cardiovascular disease, and type 2 diabetes: Systematic review and meta-analysis of observational studies. BMJ, 351, h3978.
Livesey, G. 2001. A perspective on food energy standards for nutrition labelling. British Jour-nal of Nutrition (3), 271–87.
Lynch, H.M., Wharton, C.M., & Johnston, C.S. 2016. Cardiorespiratory fitness and peak torque differences between vegetarian and omnivore endurance athletes: A cross-sectional study. Nutrients, 8 (11), E726.
Paoli, A., et al. 2013. Beyond weight loss: A review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. European Journal of Clinical Nutrition, 67 (8), 789–96.
Siri-Tarino, P., et al. 2010. Saturated fatty acids and risk of coronary heart disease: Modulation by replacement nutrients. Current Atherosclerosis Reports, 12 (6), 384–90.
Tomiyama, A.J., et al. 2010. Low-calorie dieting increases cortisol. Psychosomatic Medicine, 72 (4), 357–64.
Trepanowski, J.F., et al. 2017. Effect of alternate-day fasting on weight loss, weight maintenance, and cardioprotection among metabolically healthy obese adults: A randomized clinical trial. JAMA Internal Medicine, 177 (7), 930–38.
Widmer, R.J., et al. 2015. The Mediterranean diet, its components, and cardiovascular disease. American Journal of Medicine, 128 (3), 229–38.
Wing, R.R., & Phelan, S. 2005. Long-term weight loss maintenance. American Journal of Clinical Nutrition, 82 (1, Suppl.), 222S–25S.
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