By Barbara Quinn McClatchy – Tribune News Service

Belief that something is true without evidence — such as betting on your team to win the Super Bowl — is a presumption.

Belief that persists despite evidence to the contrary — such as refusing to believe your team lost — is a myth.

Understanding supported by good evidence — such as realizing the trophy resides with another team — is a fact. 

How do these definitions apply to our long-held beliefs about weight loss? A group of researchers looked at the evidence in a recent article in the New England Journal of Medicine. Here are a few beliefs they determined to be myth, presumption, or fact (along with a few unsolicited comments):

Small changes in how we eat or exercise over a long period of time will cause us to lose large amounts of weight. It’s a myth. Studies show that small changes result in small weight losses and large changes result in larger weight losses. Duh.

Eating breakfast on a regular basis helps guard us from being overweight. It’s a presumption, based on a few small studies done several years ago, say researchers.

Eating more fruits and vegetables will cause us to lose weight or gain less weight. This is also a presumption. Health benefits abound from eating fruits and vegetables. Yet there is no evidence that we will automatically lose weight if we eat more of these foods.

Eating breakfast or adding more vegetables to our diet does not help us lose weight unless if we also eat fewer calories. This is a fact. We can lose weight with any diet strategy if our calorie intake is low enough.

Setting realistic goals for weight loss is important so we won’t become frustrated. This is a myth, say these researchers. Really? They explain that more ambitious goals are sometimes associated with more weight loss. To which I respectively argue that “ambitious” goals can also be “realistic” goals.

Losing large amounts of weight quickly is not as good for us in the long term as slow, gradual weight loss. This is a myth, believe it or not. According to controlled clinical trials, people who lost weight quickly at the beginning of a weight loss regimen were as successful after one year as those who had lost it slowly from the beginning.

Our genes do not determine our destiny to be overweight. This is a fact — and a challenge, nutrition experts say. Think of it this way, someone once explained: What we inherit from our parents “loads the gun.” But what we choose to do — or not do — each day “pulls the trigger.”

Physical activity improves our health, regardless of what we weigh. This is a fact.