Paleolithic diet? Low fat? Atkins? Mediterranean? Confused? You are not alone. There are many diets out there, some are traditionally associated with “fads”, some have been endorsed by the FDA, and some are science / study based (at least in part). Let’s sort through some of the evidence and review 3 of the main diet types: Low Fat, Mediterranean, and Low Carbohydrate.
Low fat diets, though traditionally recommended, have shown mixed to negative results. The Women’s Health Initiative Dietary Modification Trial, a large 49,000 patient 8 year trial, unfortunately showed little benefit of a low fat diet. In the PREDMIED trial, a randomized 7447 patient trial of a Mediterranean Diet vs. a low fat diet, the Mediterranean Diet was superior in reducing heart attacks and stroke when compared with the low fat diet. During the Dietary Intervention Randomized Controlled Trial (DIRECT), which randomized patients to a low-fat, Mediterranean, or low carbohydrate diet, the low-fat diet group showed the least weight loss, and the least beneficial change in fasting plasma glucose and insulin levels. One of the concerns with low fat diets has been what replaces the fat in this diet. Often times this has been simple carbohydrates, which some feel has contributed to our obesity epidemic.
The Mediterranean Diet (which has high intake of olive oil, fruit, nuts, vegetables, along with moderate amounts of fish and poultry), shows promise. Evidence such as the PREDIMED trial and the Lyon Diet Heart Study, have bolstered the case that this is a viable alternative to the traditional low fat diets. Some of the benefits that have been linked with this diet include reduced cardiovascular disease, diabetes, depression, Parkinson’s, Alzheimer’s, and early death.
Low carbohydrate diets come in many different forms (Atkins, Zone, Paleo, South Beach). In general, these types of diets are more effective for short term weight loss than low fat diets, and less so for longer time periods. Some studies have shown reduced risk of developing diabetes, coronary artery disease, and some cancers. The type of carbohydrates consumed (by way of glycemic index or load) is important in these diets. A few recent meta-analyses of randomized controlled trials have shown that low carb diets appear to be “at least as effective as low fat diets” and that they may help reduce and maintain weight loss as well as reduce cardiovascular disease risk. However some studies have shown some opposite effects (such as small increase in incidence of cardiovascular disease) so further research is being done.
To summarize, evidence has pointed to the Mediterranean Diet and Low Carbohydrate Diets as reasonable alternatives to the traditional Low Fat Diet. When combined with an exercise program, smoking cessation, and proper preventative health care, they can be an important part of a healthy lifestyle.