There are numerous diets available. In fact, if you type the word “diet” into a Google search engine you will retrieve 130,000,000 results. There are so many diets that they can now be ranked. Recently, this was done in the US News and World Report journal (http://health.usnews.com/best-diet/best-overall-diets). Diets were ranked on the following criteria: nutritious, safe, effective for weight loss, and effective for disease prevention against diabetes and heart disease. The diets that received the highest rankings (in order) were: the DASH diet (Dietary Approaches to Stop Hypertension), the TLC diet (Therapeutic Lifestyle Changes), the Mayo Clinic diet, the Mediterranean Diet, and the Weight Watchers program. In my opinion, one diet does not fit everybody. If you are considering a diet, make sure that the food choices are healthy and that they include options that you enjoy. I have a close friend who wanted to lose 30-40 pounds before his wedding. His chosen diet was a tomato diet. For 2 months he ate daily vitamins and tomatoes. By the end of the two months, he could no longer tolerate eating tomatoes, so his daily caloric intake was very low consisting mainly of 2-3 tomatoes. He lost nearly 50 pounds. Over time his weight has returned, but his interest in eating tomatoes has not. Few studies have really compared long-term compliance and use of various popular diets. I suspect this is because dietary choices are very personal. One prior study did look at 4 diets (Atkins, Zone, LEARN, Ornish) in overweight premenopausal women and showed after 1 year, that people were more likely to stay on the Atkins diet compared to the others. Compliance to this diet led to a more sustainable weight loss (1). Recently there has been resurgence in very low calorie diets. These are not new. Many early very low calorie diets caused fatal heart rhythms when body levels of magnesium or potassium dropped in susceptible individuals. When these diets are started and vitamins and mineral supplements are used, the risk of these abnormal heart rhythms is significantly reduced. In a study of women in which at least 650 kcal/day of protein was consumed with vitamins and minerals, the very low calorie diet did not result in any abnormal heart rhythms over 6 weeks in which the diet was used (2). In general I recommend a diet with a plan to lose 1-2 pounds per month. At the same time I recommend an exercise program with an early target of 30 minutes a day. I have found that diets without lifestyle modifications, such as starting an exercise program, are rarely successful long-term. Often my patients that are moderately to severely overweight really want to jump start the process. They often are interested in a very low calorie diet of around 800 kcal/day to lose 20-30 pounds (3-5 pounds/week) quickly, and then begin a more typical diet for sustained weight loss or weight loss maintenance. Sticking to one of these diets can be a difficult task. If you look at the calories on many of the foods we eat daily, it does not take a lot to reach 800 kcal/day. In fact, many fast food sandwiches and meal options may double or triple the total you can consume in one day in one sitting. However, with some planning, less calorie dense food sources are available and can lead to a rich diet. Recently I came across an interesting article titled “30 Foods Under 40 Calories, with Recipes” in Health magazine (http://www.health.com/health/gallery/0,,20640804,00.html). The article summarizes the calories per cup of many food sources and also highlights many of their other benefits such as vitamin and antioxidant properties. As a heart specialist, I usually get asked questions such as “If I do this diet, am I safe?” or “If I do this diet, what will happen to my heart?”. My first advice to them is to begin these diets with the assistance of a physician to make sure they are receiving enough vitamins and minerals. Next, I tell them that in people that are diabetic or have high blood sugars, these diets can improve their body’s ability to utilize its’ natural insulin and their blood sugars often go down quite quickly. This is important in patients that are taking medications to control their blood sugar. Often, the doses of these blood sugar or diabetic medications need to be carefully monitored or reduced to prevent dangerous drops in their blood sugar levels. Finally, I talk about what we know happens to the heart itself. Our hearts do better long-term when our blood pressure is well controlled, we are active and exercise, our sleep apnea is treated or prevented, and our weight is optimized for our body frame. We all have different body frames. I am not a fan of the body mass index as a measure of health. Your body health is not just a product of your height and weight. Some people with small frames and bone structures will weigh less than others with a large frames and bone structures independent of their body fat content, muscle content, or daily activity. I try to reinforce to my patients that I am much less concerned about their weight than their daily activity. During a very low calorie diet there are some interesting changes to the heart. First the body levels of free fatty acids and triglycerides increase. These are byproducts of the body using its’ own energy stores rather than obtaining energy from food intake. The triglyceride content may become lower or higher in the liver, but in other organs it is accumulated. In the heart, both the bottom heart chambers begin to increase in triglyceride content (3,4). The lower heart chambers have to do two things actively. First, they have to actively pump the blood to the body. As important, the chambers have to actively relax after pumping to quickly accept the returning blood. As the triglyceride levels increase in the heart, the lower chambers become stiffer and their ability to relax lessens. The stiffer the heart becomes, the more the triglycerides accumulate in the liver. Very recently these findings were confirmed using magnetic resonance imaging (MRI) and spectroscopy of the heart in normal men that underwent a very low calorie diet of approximately 500 kcal/day (4). When these men were transitioned to a high protein diet with an exercise program, the triglyceride content in the heart returned to normal. This high protein diet was identical to the first diet, but it included the addition of 800 ml of cream daily. An interesting finding with the second diet was the liver levels of triglycerides then greatly increased. Fortunately, after beginning a very low calorie diet in women, there appears to be a long-term benefit in the health of the arteries. In 40 obese women that underwent a diet that ultimately resulted in a 16% reduction in their body mass index, the health of the blood vessels began to improve within 1 week of starting the diet and was maintained over the study period (5). Even very subtle dysfunction of our large and small blood vessels can lead to long-term high blood pressure and injury to our body organs such as the heart, kidney, pancreas, and brain. What do these studies teach us regarding diets? First, with careful supplementation of vitamins and minerals the risk of developing abnormal heart rhythms becomes very low. Next, the heart is affected adversely in the setting of severe calorie restriction. However, the changes that develop appear to be temporary and reverse when a higher calorie diet is resumed. If you are considering one of these diets, look at it as a bridge to a long-term diet that you will enjoy and can consistently use. Since we can visualize structural changes to the heart very early after severe calorie restriction, I would recommend not repeatedly using these diets to maintain your weight over time. Long-term maintenance of weight should be from a very diverse healthly diet of whole food sources that contain vitamins, minerals, proteins, etc, and lifestyle modifications that include exercise and increasing daily activity. Sources 1. Gardner CD, Kiazand A, Alhassan S, Kim S, Stafford RS, Balise RR, Kraemer HC, King AC. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A TO Z Weight Loss Study: a randomized trial. JAMA. 2007 Mar 7;297(9):969-77. 2. Moyer CL, Holly RG, Amsterdam EA, Atkinson RL. Effects of cardiac stress during a very-low-calorie diet and exercise program in obese women. Am J Clin Nutr. 1989 Dec;50(6):1324-7. 3. Hammer S, van der Meer RW, Lamb HJ, Schär M, de Roos A, Smit JW, Romijn JA. Progressive caloric restriction induces dose-dependent changes in myocardial triglyceride content and diastolic function in healthy men. J Clin Endocrinol Metab. 2008; 93(7):2702-8. 4. Widya RL, Hammer S, Boon MR, van der Meer RW, Smit JW, de Roos A, Rensen PC, Lamb HJ. Effects of Short-Term Nutritional Interventions on Right Ventricular Function in Healthy Men. PLoS One. 2013 Sep 23;8(9):e76406. 5. Mavri A, Poredoš P, Suran D, Gaborit B, Juhan-Vague I, Poredoš P. Effect of diet-induced weight loss on endothelial dysfunction: early improvement after the first week of dieting. Heart Vessels. 2011; 26(1):31-8. CREDIT: Thinkstock
