The Health Benefits of a Plant-Based Diet

More people than ever are eating a whole-food, plant-based diet. Studies show that it is better for our bodies and better for the planet—but it isn't always easy.


"A Plant-Based Life" by Micaela Cook Karlsen will teach you how to take advantage of shopping tips, pantry lists, menu plans, and more than 100 mouth watering recipes.

Photo courtesy AMACOM Books

Content Tools

Whether you're taking your first steps on this path to wellness or recommitting yourself to success, let A Plant-Based Life (AMACOM Books, 2016) by author Micaela Cook Karlsen be your guide. Her program enables you to set your own pace and stay the course—without relying on willpower. Drawing on personal experience and the latest research, she reveals how to: find and sustain your motivation; gradually add more whole, plant foods into your diet, crowding out less nutritious fare; break old food addictions and establish new habits and translate favorite recipes to create delicious, nourishing meals. Especially valuable are directions for navigating roadblocks. Here you'll find strategies for getting family members on board and for allaying friends' concerns about your food choices with evidence-based nutrition information.

The scientific evidence that demonstrates and supports the benefits of a plant-based diet is growing all the time, and the most dramatic aspect is that the effects not only prevent people from getting sick but, for certain serious conditions, the food they eat can also make them well.

Making people well is not something that medication for chronic disease has ever accomplished, and perhaps it never will. This is not for lack of effort on the part of drug developers or doctors, but the medications for chronic disease manage symptoms rather than treat the cause of the illness. Many studies suggest that when you look at the rates of adherence for medication, they are pretty dismal — many patients struggle to take their prescriptions as directed, and quitting altogether is common! And who can blame them? Often, medications have side effects that make them feel worse, not better.

In contrast, many people who switch to a whole food, plant-based diet are highly motivated to continue because suddenly, perhaps for the first time in a long while, they feel good! For heart disease and type 2 diabetes, there are countless examples of individuals who, by changing their diet, have been able to reduce or discontinue their medications under their doctor’s supervision. These outcomes are consistent with what has been demonstrated in the peer-reviewed research data on people who eat plant-based diets over the long-term, as well as intervention studies in which participants are assigned to a plant-based eating plan and their results are compared with other diets. This information has begun to permeate the field of medicine, as increasingly more physicians now support plant-based diets as the foundation of medical treatment for a variety of chronic diseases.

The feelings of sustained energy and longer-lasting satiety (feeling full after a meal) are only the beginning of the many benefits of a plant-based diet. While you no doubt have your own reasons for reading this book, in the next few pages we’re going to cover some of the demonstrated health benefits for the prevention and/or reversal of four major chronic health problems that people in developed countries currently face: weight issues (which impact many conditions and diseases), type 2 diabetes, cardiovascular disease (heart disease), and cancer. For each, we’ll take a look at the typical outcomes for plant-based eaters, delve into some background as to what is going wrong when these conditions develop, and explain how a plant-based diet can remove the source of the problem. This information will not only provide you with a deeper understanding of the positive effects of this diet, but may also serve to inform your conversations with your family, friends, and doctors. The results speak for themselves!

Weight Issues

How would you like to eat until you felt full every time you were hungry, maintain a healthy weight, and never have to worry about counting calories? That is what can be gained by eating a plant-based diet. Plant-based eaters, both vegetarians (who eat no meat), and vegans (who eat no animal foods at all), are more likely to be at their normal weight compared to omnivores.They’re also more likely to gain less weight over time — the nemesis of many aging adults.

Both overweight children and adults also lose weight more easily eating a plant-based diet than other types of diets, and this is true even without controlling portion size. In an exciting experiment published by researchers at the University of South Carolina, five different diet groups of overweight adults were given guidelines for the kinds of foods to eat, but without any portion control. In other words, they could eat as much as they wanted — they could eat until they were satisfied — and the individuals in the vegan group lost more weight compared to pesco-vegetarians (plant foods plus fish), semi-vegetarians (reduced animal food), and omnivores (plants and animals)!

The total energy you use on a daily basis is primarily determined by three factors: your basal metabolism, which reflects the minimum level of energy you need to keep your body alive while at rest — breathing, eating, digesting, keeping your heart and other organs working, maintaining your immune system, and performing countless other jobs; your level of physical activity; and adaptive thermogenesis (how much of the food you eat is converted to heat and released). Of course, it’s possible to eat less than the minimum level of energy you need to stay alive; that’s called negative energy balance, and it’s what happens when you lose weight because you are using energy that your body has previously stored as fat.

What’s Going Wrong?

You create those fat stores when the energy you take in (in the form of food) is greater than the energy you use. This is called positive energy balance, and it’s no secret that this constitutes a major problem for many people. Currently in the United States it’s less common to be at a healthy weight than it is to be overweight. Two-thirds of all Americans are overweight and half of those are obese; sadly, almost one-third of children in the United States are overweight, with an additional 16 percent being obese; globally this disturbing trend continues in many other countries.

Beyond the immediate personal discomforts, physical and emotional, that can come with being overweight, excess pounds also put you at greater risk for a host of chronic diseases, especially the three we’ll cover next — type 2 diabetes, cardiovascular disease, and cancer. Most adults in the United States continue to gain weight as they age, averaging almost half a pound per year after age 20. If left unchecked, this pattern increases the risk of developing metabolic syndrome (MetS), type 2 diabetes (T2D), heart disease, cancer, sleeping problems, kidney disease, depression, asthma, and osteoarthritis.

Gaining weight is easy in the modern world because the majority of the foods we’re consuming are very energy-dense, meaning that when compared to the amount of space they take up in the stomach, they pack a lot of calories. We’ll discuss this further in Step Three, but suffice it to say that animal foods like meat, cheese, eggs, and butter; processed foods like soda, cookies, chips, candy, white flour products; and sugary or oily snacks (like the colorful spread of packaged “foods” you might see for sale in a gas station or the middle aisles of a grocery store) make it easier than ever to eat more calories than you need, usually without realizing it. This is the source of the disappointing results of research studies that attempt to produce weight loss with physical activity but without changing diet; if you were to choose either changing your diet or exercising more, you would get a much bigger bang for your buck by choosing to eat different foods than by trying to exercise off what you’ve eaten.

Don’t get me wrong — exercise is important and brings a lot of health benefits, like reduced risk of other diseases, but when it comes to achieving a healthy weight, you can’t do it without adjusting your diet. It’s just too easy to eat larger portions of foods that are more energy dense, even without realizing it, and the delicate balance of homeostasis (the steady-state of dynamic equilibrium) that our bodies work so hard to maintain can be thrown off in a heartbeat. Since one pound of fat contains about 3,500 calories, you need only 10 unburned calories per day to gain a pound over the course of a year. Most adults are eating several hundred calories more than they need, which provides that excess weight, even after the body’s automatic adjustments to try to burn the extra energy. Over time, this leads to a steady weight gain in adulthood.

Although not everything we eat comes in 100 gram quantities, Table 1 illustrates how much more exercise is required to burn off energy-dense foods — 884 calories of fat is about seven tablespoons, which sounds like a lot but can easily be worked into a meal if you’re not paying attention by choosing fatty foods, sautéing food in oil, buttering your bread, and eating almost any typical dessert.

How Can a Plant-Based Diet Help?

While most adults gain weight as they age, this is not part of healthy aging, and it doesn’t have to happen to you! The foods that make up a plant-based diet (whole grains, legumes [peas, beans, and lentils, for example], fruits, vegetables, and limited amounts of nuts and seeds) are dense in vitamins and minerals but contain plenty of fiber (mostly indigestible complex carbohydrates—what many people call “roughage”). Because for the most part we don’t digest fiber, it doesn’t add any calories to the diet. This is why you can fill up eating whole plant foods and still consume fewer calories.

Fiber provides bulk as well as slows the emptying of your stomach. This helps you feel full longer, causing you to want to eat less. Fiber also makes it physically impossible to overeat, because the added bulk activates the “stretch receptors” in the stomach. These receptors signal the brain that you’ve had enough. Animal foods contain no fiber (meat and dairy), and processed foods have either had fiber removed (white flour) or had energy added in the form of fat and sugar without an increase in fiber (French fries). So a meal of a cheeseburger, white bun, and fries packs a lot of calories but it doesn’t fill you the way a meal of brown rice, vegetables, and beans does, even though the plant meal has a lot less energy! Most people starting to eat a whole food, plant-based diet for the first time find that excess weight just slides away, even without increasing their level of exercise. This is not only true for people who are already plant-based, but also for those who step it up a notch and take out the added fat as well.

Type 2 Diabetes and Cardiovascular Disease

A plant-based diet is the only treatment that has been shown to reverse our top culprits of disability and mortality. More plant food consumption predicts lower blood pressure, improved blood lipids, lower risk of developing type 2 diabetes, and a lower risk of death from cardiovascular disease (CVD). But it doesn’t stop there. Physicians who prescribe plant-based diets as treatment get results unmatched by medication. A word of warning here: It’s very important to talk to your doctor before changing your diet if you are taking any medication, especially if it is a medicine that lowers your blood pressure or controls your blood sugar. Dr. Neal Barnard, from the Physicians Committee for Responsible Medicine, in collaboration with George Washington University School of Medicine, has conducted studies of type 2 diabetics and found that medication changes are frequently required after switching to a low-fat, vegan diet. The effect of totally plant-based eating is so rapid that your blood sugar can drop to dangerously low levels if you are taking medication at the same time. 

Imagine being told it would best to go home and prepare for the end because there was nothing more that doctors could do for you. And if your advanced stage heart disease was being treated only with statins, stents, medications, or surgery, you would probably be right to do so! Fortunately, the work of two notable physicians, Dr. Caldwell Esselstyn at the Cleveland Clinic and Dr. Dean Ornish at the University of California, has demonstrated the efficacy of reversing damage to arteries from the Western diet by switching patients to a low-fat, vegan diet. In fact, at the time Dr. Esselstyn began his work with diet, most of his patients had been given no other options by their doctors but to get their affairs in order.

What’s Going Wrong?

CVD is the number one killer among chronic diseases in the United States and mortality from diabetes trails closely behind at number seven; these two diseases annually claim 610,000 and roughly 70,000 lives, respectively. These are not just statistics. A diagnosis of either one often comes with restrictions on physical activity, fear of overexertion, and stress from the prescribed treatments. The combination of these two diseases presents further cause for concern, as both risk of stroke and mortality from heart disease are two to four times greater among adult diabetics. That means a lot of people have elevated risk for CVD — 11.3 percent of adults in the United States are estimated to have diabetes and 35 percent are estimated to have prediabetes; these figures jump to 50 percent and 26.9 percent, respectively, of adults over age 65.

Cardiovascular disease is a general term that covers a range of problems in different parts of the body relating to the heart and all the blood vessels. One problem, a stroke, is brain cell damage from lack of oxygen due to reduced or blocked blood flow in the brain. Another problem, erectile dysfunction, or impotence as many people call it, is usually one of the first signs of heart disease — the tiniest blood vessels are the first to go (men experiencing this problem might want to take extra note of the fact that the condition is reversible).

Type 2 diabetes, a closely related problem, is a condition in which our ability to use glucose (sugar), the simplest form of carbohydrate, for fuel is disrupted. Normally, the beta cells of the pancreas produce insulin, which is often compared to the key that unlocks the door to our cells so energy can be brought inside. Insulin ushers the glucose into our cells from the bloodstream, making it possible for us to use the glucose in our blood.

Type 2 diabetes used to be called “adult-onset diabetes,” but the term is no longer used because so many children have it. Type 2 diabetes is a common and rapidly growing problem due to diet and lifestyle. In diabetics, the pancreas still makes insulin but either it’s not enough or the cells do not recognize it. This is a state called insulin resistance. If your cells are insulin resistant, at first the pancreas will try to produce extra insulin to catch up with your mounting blood sugar levels. This may work for a while, but if your cells aren’t allowing the insulin to work, the pancreas can wear out, start producing less insulin, and the sugar you eat will stay in the bloodstream at even higher levels. If your cells can’t access the fuel, you’ll have trouble producing the energy you need, which leads to fatigue and a variety of problems. Eventually, the complications that develop can range from depression to amputations to death.

Both conditions are caused by eating a diet high in animal foods and low in plant foods, diets high in total fat, saturated fat, and refined carbohydrates. The saturated fat increases the body’s own production of cholesterol past the point at which the body can keep up and eliminate it. The body tries to deal with the problem by storing the cholesterol in little pockets here and there, wherever it can. Plaque forms as remnants of low-density-lipoprotein (LDL, or “bad”) cholesterol are sucked through the cells lining the arteries and consumed by immune cells called macrophages, whose central job is this “cleanup” of LDL remnants. Once these macrophages ingest the LDL, they become foam cells (so called because they are filled with whitish cholesterol that looks like foam) and they die. The accumulation of dead cells builds up under the surface of the endothelial cells that line the blood vessels. At some point, this thin lining wears away due to the pressure of pumping blood. When this happens, the rupture causes a blood clot, which can then cause a stroke or heart attack. A rupture is more likely than a gradual blockage due to plaque buildup, which is why the first symptom of heart disease for many patients is a fatal heart attack. Type 2 diabetics are at an even greater risk for CVD because of a condition known as diabetic dyslipidemia — essentially they tend to have even more of these LDL remnants, which promotes the process of plaque formation even faster.

Excess fat and sugar consumption both raise blood triglycerides (the fat present in our blood), which can clog the insulin receptor cells that are supposed to enable insulin to work, thus promoting insulin resistance. The body is then even less equipped to handle the sudden rush of blood sugar that takes place when you consume pastry, white flour, cookies, or sugary drinks. This leads to elevated blood sugar levels over time, and eventually to diabetes.

How Can a Plant-Based Diet Help?

Whole food, plant-based diets are naturally low in all of the components known to promote plaque formation in the blood vessels or cause insulin receptor cell failure. These include trans fat, saturated fat, refined carbohydrates, dairy products, and red meat. At the same time, whole food, plant-based diets are naturally rich in all the nutrients and foods that have been associated with decreased risk — more fruits and vegetables, whole grains, legumes, and nuts. Not only can they help us avoid developing CVD and type 2 diabetes, but they also make excellent health and wellness possible as we age. 

When people with advanced stage heart disease start eating a low-fat, whole food, plant-based diet, the results are remarkable. Within weeks, most patients can notice an improvement of certain symptoms they had been experiencing—such as shortness of breath and angina (chest pain). Over time, they can also expect that the damage done to their arteries by their former diet will gradually be repaired. Dr. Neal Barnard’s pioneering work in treating type 2 diabetes with plant-based diets has now been documented in multiple studies. Within a time frame of weeks or months, type 2 diabetics are able to reduce or eliminate medication. Just think of the improved quality of life and cost savings, as well as the blessing of not being ill!


Although cancer is a more complex disease than being overweight or having diabetes or heart disease, the evidence is strong that whole food, plant-based eating is the best protection and the best dietary choice to complement cancer treatment. Researchers have estimated that the major of portion of cancers are lifestyle related — another way of saying preventable — with a substantial portion preventable directly by diet. Red meat and dairy products, not just smoking and alcohol consumption, are independently associated with cancer risk, and plant-eaters have lower rates of cancer even with very small increases in animal food intake. The China Project, a research survey of 6,500 adults in 65 counties in China conducted by Dr. T. Colin Campbell and his collaborators from Oxford University and the Chinese government, found there was no threshold of animal food consumption that was not associated with increased risk for cancer mortality and other chronic disease in a comprehensive survey of dietary and lifestyle risk factors in China. This means the more plants we eat, the better.

What’s Going Wrong?

There are many potential mechanisms that indicate the effect of animal foods on cancer risk, but one of the most striking and interesting, as it relates directly to plant-based patterns, is the seeming effect of animal protein on promoting cancer development. First, cancer is initiated — meaning that a genetic mutation occurs. If the immune system doesn’t catch this mutation and repair it, it may reproduce and continue on to the promotion stage, in which cancerous cells and eventually a tumor, grow. 

One of protein’s major roles is cell growth and repair, but cancer occurs when cell growth is unchecked and the normal signals for cell death are overridden. Dr. Campbell’s experiments in the laboratory demonstrated decades ago that increased levels of animal protein, but not plant protein, had the ability to promote the growth of cancer — and, perhaps even more interesting, he showed that decreasing the level of animal protein in the diet could reverse the growth of cancer after it had been initiated. His team replicated these experiments many times and in many ways.

The critical threshold in rats (who need about the same amount of protein as humans) at which excess animal protein starts to promote cancer growth seemed to be about 10 percent. At 5 percent of total calories, protein had no effects on rats who were predisposed to cancer, meaning they had been previously exposed to chemical toxins or viruses. At 20 percent of total calories, precancerous cells formed and grew more quickly than at 5 percent. When the researchers switched the diet back and forth between 5 percent and 20 percent and then back to 5 percent protein calories, they saw the cancer cells first stay dormant, then grow, and then recede. Most of us, especially those of us eating animal food, are eating much more than 10 percent protein.

Similar findings on the risk associated with higher protein consumption were demonstrated in an exciting 2013 study from the National Nutrition and Health Examination Survey (NHANES). Their analysis of protein consumption among adults in the United States showed that a higher intake of protein among adults under 65 was associated with higher rates of cancer and higher overall mortality. The researchers found that this association was most likely due to the animal protein, but not to the plant protein these individuals consumed. This analysis was paired with a series of animal experiments and demonstrated multiple pathways by which protein might promote the growth of cancer, confirming earlier experimental work.

How Can a Plant-Based Diet Help?

These kinds of results are important, because crossing above the range of 10 percent protein consumption is well within the range of what most people are eating; the average protein intake is between 11 and 22 percent. Contrast this to cancer research on chemical carcinogens and environmental toxins; these are usually considered a demonstrated danger at levels much higher than humans normally encounter them.

Eating a whole food, plant-based diet will naturally give you between 10 and 12 percent of your calories from protein without even trying! There is no need to make a point of “getting enough protein in your diet” — it happens easily and naturally, making this a risk factor well within your realm of control. Physicians are beginning to recommend plant-based diets to complement cancer treatment; there have already been some encouraging findings regarding the use of diet as the treatment itself. Dr. Dean Ornish has demonstrated in a well-known and remarkable randomized controlled intervention trial that a low-fat vegan diet is able to delay or even eliminate the need for treatment of prostate cancer among patients who are undergoing active surveillance, known as the “watch and wait” approach. After two years, 27 percent of the control group, but only 5 percent of the plant-based group, had undergone conventional prostate cancer treatment. While this didn’t work for every patient, for those whom it did, imagine the relief at avoiding chemotherapy, radiation, and surgery!

A Plant-Based Life: Your Complete Guide to Great Food, Radiant Health, Boundless Energy, and a Better Bodyby Micaela Cook Karlsen and published by AMACOM Books © 2016 Micaela Cook Karlsen. All rights reserved. Division of American Management Association; 1601 Broadway, New York, NY 10019.