“One cannot think well, love well, sleep well, if one has not dined well.” – Virginia Woolf

For 2.5 million years, our ancestors ate only what they could hunt and gather themselves. Every food item was raw, fresh, packed with vitamins and minerals, and had no refined sugar or salt. As we evolved, natural selection showed preference for humans eating this type of diet. Over the years, our health and survival as a species became genetically dependent on it.

Our genetic makeup is 99.995 percent identical to that of our Paleolithic ancestors, yet our diet has changed dramatically. In fact, 70 percent of our diet consists of foods that were not even available to our Paleolithic ancestors. The result is that two-thirds of all Americans are now considered to be overweight or obese, one-third have high blood pressure, 64 million have cardiovascular disease, and 11 million have Type II diabetes.

Termed “the diseases of civilization,” these health conditions are the direct result of the food we eat.

There are seven crucial nutritional characteristics of the diet our hunter-gatherer ancestors ate that are missing from our modern diet: (1) its glycemic load, (2) its fatty-acid composition, (3) its macronutrient composition, (4) its micronutrient composition, (5) its acid-base balance, (6) its sodium-potassium ratio, and (7) its fiber content. These deviations are responsible for the overwhelming majority of today’s health problems. But by eating a diet that optimizes each of these missing elements, you can greatly improve your chances of living a longer, disease-free life.

Here’s how to do it:

1. Glycemic Load

Our modern Western diet of high-glycemic refined grain and sugar products has a much higher glycemic load (a measure of the blood glucose raising ability of foods) than our ancestors’ diet. Sugars and refined grains now represent more than 39 percent of the calories in the typical U.S. diet, a drastic change that has occurred only within the last 200 years – hardly a blip on the evolutionary time scale. Long-term consumption of high-glycemic foods causes insulin resistance, which is the main factor underlying most degenerative diseases. Removing high-glycemic foods from your diet and filling up on low-glycemic foods is one of the most important things you can do to maintain your ideal weight. It can also help you live a longer life and (more important) enjoy greater health and more capacity for activity in your later years.

2. Fatty-Acid Composition

Fight heart disease, reduce your risk of cancer, and lose weight by consuming enough of the right fats. Eat more monounsaturated fats like olive oil and omega-3 polyunsaturated fats from fish or fish oil supplements, and cut back on vegetable oils and conventionally raised meats.

Our ancestors got most of their dietary fat from wild game. Because wild game meat is much leaner and is a richer source of monounsaturated and omega-3 polyunsaturated fatty acids than our modern feedlot animal meat, our ancestors evolved with a different ratio of these fats than we are consuming today. Experts estimate that our ancestors consumed approximately two omega-6 fat molecules for every one omega-3 molecule, a ratio of 2:1. Today, most people consume an unnaturally distorted ratio of 10 to 20 omega-6 fats for every one molecule of omega-3.

Trans-fats and saturated fats lead to elevated LDL cholesterol, atherosclerosis, and chronic inflammation. A high omega-6:omega-3 ratio also promotes chronic inflammation, a characteristic of many common degenerative diseases.

3. Macronutrient Composition

Add more protein to your diet. This can improve your blood-lipid profiles and help you feel fuller and burn more calories. The best sources of protein are fish, grass-fed beef and eggs.

The proportion of calories we receive from the three main macronutrient groups – carbohydrate, protein, and fat – are also out of sync with how our bodies evolved to function optimally. The typical U.S. diet approximately mirrors USDA recommendations: Around 52 percent of daily energy comes from carbohydrates, 33 percent from fat, and roughly 15 percent from protein. Hunter-gathers received a significantly higher amount of calories from protein (estimated at between 19 and 35 percent) at the expense of calories from carbohydrates (22 to 40 percent).

4. Micronutrient Density

Ensure that your body is nourished and help your stomach feel full and satisfied, without gaining weight, by increasing the nutrient-density of your diet. To do this, try to eat one-third of your calories in the form of fruits and vegetables.

One of the results of a glut of refined grain, sugar, and vegetable oil in our modern diet is the displacement of nutrient-dense foods. Vegetable oils and refined sugars have very few vitamins, minerals, and phytochemicals in them, but now contribute more than 36 percent of energy in the average American diet.

5. Acid-Base Balance

Getting 35 percent of your calories from fruit and vegetables can also help restore your body’s acid-base balance.

After digestion and metabolism, all the foods we eat release either acidic or basic substances into the circulatory system. Vegetables, fruit, tubers, roots, and nuts are all net-base-producing, whereas diary products, fish, meat, eggs, cereal grains, and salt are net-acid-producing. With a heavy reliance on fruits and vegetables, our hunter-gatherer ancestors had a net-base-producing diet throughout our evolution.

Today, we depend on dairy products and cereal grains for roughly 35 percent of our calories at the expense of fruit and vegetables, resulting in a modern diet that is net-acid-producing. Switch back to a more balanced diet and you may reduce your risk of kidney malfunction, osteoporosis, age-related muscle wasting, kidney stones, hypertension, and exercise-induced asthma.

6. Sodium-Potassium Ratio

Balance your sodium intake with potassium to reduce your risk of developing disorders like hypertension, stroke, kidney stones, osteoporosis, gastrointestinal-tract cancers, and asthma. By avoiding packaged foods in favor of fresh ones, you’ll cut a majority of the excess sodium from your diet.

The ideal sodium to potassium ratio is less than 1 – and this electrolyte balance is critical for normal cell function. The exorbitant amount of sodium Americans consume in processed foods and by voluntarily adding it to prepared foods (options not available to our ancestors) far outweighs the potassium we ingest from fruit and vegetable sources. Potassium concentrations in vegetables are four times those in milk and 12 times those in grains. Fruit has, respectively, approximately two and five times the potassium concentrations in milk and grains.

7. Fiber

Add more fiber to your diet. This simple addition can help you avoid disorders connected to low dietary fiber, like constipation, appendicitis, hemorrhoids, varicose veins, diverticulitis, hernia, and gastro-esophageal reflux. If you replace refined sugars and oils, grains, dairy products, and processed foods with fruits and vegetables, you will ingest around 42 grams of fiber a day.

It does not take an education in nutrition to know that the typical American diet is low in fiber. We get about 15 grams per day when we should be getting around 25 to 30 grams a day. Vegetables are by far the best source of fiber, and they provide eight times the amount of fiber in whole grains, on an energy basis. Soluble fibers (fruit/vegetables) reduce total and LDL cholesterol and slow the emptying of the stomach – which reduces the appetite and total calories consumed.

Eat Good Food

Eating well can be the key to a long and healthy life. Diet-related chronic diseases represent the single largest cause of morbidity and mortality in most Western countries. Virtually all the so-called diseases of civilization have multiple dietary causes, but the solution is the same: Eat a diet based on fruit, vegetables, fish, and naturally raised or wild meat, and avoid excess sugar, grains, dairy, and processed vegetable oils.

This is the diet mankind evolved to eat … and it will keep you healthy for years to come.

[Ed. Note: During the past two decades, Dr. Loren Cordain has researched the effects of diet on human health, specifically examining the links between modern diets and disease. In addition to authoring numerous scientific articles and three popular books, he is the author of the e-book The Dietary Cure for Acne and publisher of The Paleo Diet Newsletter .]