I have a colleague who follows a very strict semi-vegetarian diet. He eats mostly fruits and vegetables, whole grains (oatmeal, brown rice, and whole wheat pasta), beans (including lentils), and nuts.

He limits his consumption of animal products to chicken and egg whites. Most everything he eats is plain – no dressings, sauces, or seasonings – and most meals contain only a few ingredients.

He credits this diet, along with daily exercise, for his healthy weight, low blood pressure and cholesterol, and excellent overall health.

But such a strict diet poses some challenges, like eating away from home where he can’t control meal preparation. For this reason, he rarely eats out.

I would agree that his diet has positive effects on his health. But does this mean that such a strict diet is necessary? Is it possible to eat a less restrictive diet and still be healthy?

It turns out that you don’t have to eat a perfect diet to lose weight, lower your cholesterol, or feel better. In fact, even relatively small changes in what you eat can have a big impact on your health.

For example, you can lose weight simply by reducing your portion sizes, without changing the foods you eat.

You can lose more weight by making bigger changes to your diet such as reducing fat and sugar intake and eating more fruits, vegetables, and whole grains.

To put it another way, doing a little can have big benefits; doing more leads to even bigger changes.

Several studies show that a more restrictive a diet has greater effects on health. One is the Seven Country Study, which looked at lifestyle and cardiovascular disease in seven countries around the world.

One finding was that a higher intake of saturated fat was linked with higher total cholesterol.

In Finland, where the typical diet includes 20 percent of calories from saturated fat, the average blood cholesterol was 265 mg/dl.

By contrast, the Japanese consume only 5 percent of their calories from saturated fat and their average blood cholesterol was 165 mg/dl.

The take-home message is that the further your reduce your saturated fat intake the lower you may expect your blood cholesterol to go.

Another example is the Lifestyle Heart Trial, a landmark study that demonstrated that comprehensive lifestyle changes can actually reverse heart disease.

Patients who followed a strict vegetarian diet, three hours per week of exercise, and daily stress management sessions experienced regression of coronary artery disease and favorable changes in blood pressure and blood lipids.

Patients who followed a typical diet got worse. Furthermore, within the experimental group, the better the adherence to the treatment, the greater the extent of the changes.

While the results are remarkable, this study has been criticized because the lifestyle changes are so strict.

The good news is that you can experience health benefits from making less extreme changes.

Combining dietary modifications with exercise will result in greater benefits. In fact, if you exercise regularly you can achieve the same health benefits without making such big changes to your diet.

For example, someone who exercises every day can get away with eating more without gaining weight.

The trick is to find a balance between what you eat and how active you are.

A good goal is to make small steps toward improving your diet and activity by reducing portion sizes, eating more fruits, vegetables, and whole grains, and dedicating a minimum of 30 minutes each day to being active.

You may be surprised how much you will benefit from these simple changes.

Brian Parr, Ph.D., is an associate professor in the Department of Exercise and Sports Science at USC Aiken where he teaches courses in exercise physiology, nutrition and health behavior.