We define myths as beliefs held to be true despite substantial refuting evidence, presumptions as beliefs held to be true for which convincing evidence does not yet confirm or disprove their truth

The field of health and nutrition is rich in cognitive pollution and false knowledge. Everyone has a view and empirical data is manhandled to conform with pre-existing but unvalidated assumptions. From Myths, Presumptions, and Facts about Obesity by Krista Casazza, et al there is an effort to synthesize what is known and unknown. They make a distinction between myths and presumptions.

We define myths as beliefs held to be true despite substantial refuting evidence, presumptions as beliefs held to be true for which convincing evidence does not yet confirm or disprove their truth, and facts as propositions backed by sufficient evidence to consider them empirically proved for practical purposes.

Here are their list of myths and presumptions.

Myth number 1: Small sustained changes in energy intake or expenditure will produce large, long-term weight changes.
Myth number 2: Setting realistic goals for weight loss is important, because otherwise patients will become frustrated and lose less weight.
Myth number 3: Large, rapid weight loss is associated with poorer long-term weight-loss outcomes, as compared with slow, gradual weight loss.
Myth number 4: It is important to assess the stage of change or diet readiness in order to help patients who request weight-loss treatment.
Myth number 5: Physical-education classes, in their current form, play an important role in reducing or preventing childhood obesity.
Myth number 6: Breast-feeding is protective against obesity.
Myth number 7: A bout of sexual activity burns 100 to 300 kcal for each participant.
Presumption number 1: Regularly eating (versus skipping) breakfast is protective against obesity.
Presumption number 2: Early childhood is the period in which we learn exercise and eating habits that influence our weight throughout life.
Presumption number 3: Eating more fruits and vegetables will result in weight loss or less weight gain, regardless of whether any other changes to one's behavior or environment are made.
Presumption number 4: Weight cycling (i.e., yo-yo dieting) is associated with increased mortality.
Presumption number 5: Snacking contributes to weight gain and obesity.
Presumption number 6: The built environment, in terms of sidewalk and park availability, influences the incidence or prevalence of obesity.

The authors also share nine facts, propositions where there is sufficient evidence to consider them empirically proved.

Fact 1: Although genetic factors play a large role, heritability is not destiny; calculations show that moderate environmental changes can promote as much weight loss as the most efficacious pharmaceutical agents available.
Fact 2: Diets (i.e. reduced energy intake) very effectively reduce weight, but trying to go on a diet or recommending that someone go on a diet generally does not work well in the long-term.
Fact 3: Regardless of body weight or weight loss, an increased level of exercise, increases health.
Fact 4: Physical activity or exercise in a sufficient dose aids in long-term weight maintenance.
Fact 5: Continuation of conditions that promote weight loss promotes maintenance of lower weight.
Fact 6: For overweight children, programs that involve the parents and the home setting promote greater weight loss and maintenance.
Fact 7: Provision of meals and use of meal-replacement products promote greater weight loss.
Fact 8: Some pharmaceutical agents can help patients achieve clinically meaningful weight loss and maintain the reduction as long as the agents continue to be used.
Fact 9: In appropriate patients, bariatric surgery results in long-term eight loss and reductions in the rate of incident diabetes and mortality.