Exercising every other day (at least) is needed to maintain optimal insulin sensitivity.
A good rule of thumb is, don't go two days in a row without meaningful exercise. That means you will need to do significant aerobic exercise at least 4 days per week.

According to McCarty, the "fat poisoning" that underlies insulin resistance syndrome arises from the interaction of obesity, a fatty diet, and a sedentary lifestyle that augments muscle insulin resistance while promoting weight gain. Fatty meals, fatty bodies, and poor exercise habits are the terrible trio that conspire to induce this syndrome.

Conversely, some relatively lean people can become insulin resistant. These people are not fat overall but often have an increased amount of fat in deep abdominal (visceral) fat stores. These people can benefit from even a modest amount of fat loss. Elderly people who wouldn't strike you as fat often prove to be insulin resistant. If you look more carefully, you'll note that they have a bit of a pot belly and that may be at the root of their problem. Insulin Resistance Syndrome is progressively increasing as excessive consumption of calorie-dense foods, coupled with sedentary habits, propels an epidemic of obesity in America.

The amount of carbohydrate you eat in a meal affects the post-meal rise in blood glucose. When you consume foods with a relatively low caloric density such as most whole (undried) fruits, vegetables, beans, and tubers, you tend to eat fewer total carbohydrate calories at one sitting, so post-meal glucose levels are unlikely to be excessive. On the other hand, the white flour, sugary and oily foods popular in our society are calorie dense and also usually have a high glycemic index. Pasta, because it digests slowly, is an exception to this rule. Although potatoes have a high glycemic index, they have a very high water content and thus are calorically rather dilute, as long as you don't pile on the butter or sour cream and only have them sparingly.

2/3 of U.S. adults are overweight and childhood obesity is ballooning
Poor diet and physical inactivity, blamed for 400,000 deaths a year, may soon overtake smoking as the No. 1 cause of preventable death. Americans should cut harmful fats, get more exercise and watch their weight under a new set of U.S. government dietary guidelines being written by nutrition experts. New rules include cutting consumption of saturated fat, trans fat and cholesterol.

It's sad that people will make almost any lifestyle change asked of them when their health has already failed and they are warned that they must make a change if they are to survive regardless of the medical intervention being planned to keep them alive. What has to happen for people to realize that making healthy lifestyle changes, BEFORE health problems develop, optimizes their chances for living a long and healthy life? Pass this information on to someone you love.