A Mediterranean-type diet has lots of vegetables, fish rather than meat and olive oil instead of butter. Such a regimen has been shown to protect the heart. Could a Mediterranean diet also help you control your weight? A fascinating study in nonhuman primates suggests that it might (Shively et al, Obesity, online April 23, 2019).
The Mediterranean Diet Study in Monkeys:
The researchers divided 38 monkeys into two groups. The monkeys then ate either Western-style or Mediterranean-type diets formulated to mimic human eating patterns. Over the course of 38 months, roughly equivalent to nine human years, the monkeys on the Western diet ate more than they needed and gained weight. Those given a Mediterranean diet ate less.
By the end of the study, the animals eating a Mediterranean diet had lower body weight and less body fat. In addition, they had lower levels of triglycerides circulating in their blood. Monkeys on the Mediterranean diet were also much less likely to develop non-alcoholic fatty liver disease. Unfortunately, this is an increasingly prevalent problem among humans in the US.
It is far more difficult to study the effects of diet in human beings. People don’t always follow the exact regimen the investigators specify. In observational studies, other factors besides diet might account for the differences between various groups. However, this study is not the first to suggest that following a Mediterranean diet might help you control your weight.
How Olive Oil Might Help You Control Your Weight:
The PREDIMED study suggested that extra-virgin olive oil or nuts need not lead to weight gain. Nearly 7,500 overweight adults at high risk of heart disease participated in this study for five years. The volunteers followed one of three experimental diets. One was a low-fat diet similar to the one recommended by the American Heart Association. Another was a Mediterranean diet with extra olive oil (four tablespoons daily). Finally, the third was a Mediterranean diet with extra nuts (a handful a day of walnuts, almonds or hazelnuts). These foods were provided. The participants were not advised to restrict their calories or increase their physical activity.
The Mediterranean diets that were studied were high in fat, with about 42 percent of calories from fat, but the fat was primarily from vegetable sources. Perhaps surprisingly, people in all three groups lost a little weight rather than adding pounds (or more properly kilos, since they were in Spain).
People Eating Olive Oil Did Best:
Those in the olive-oil group lost a bit more, a difference that was modest but statistically significant (Beulen et al, Nutrients, Dec. 19, 2018). Moreover, people in the olive-oil group had smaller waist sizes after five years (Estruch et al, The Lancet Diabetes & Endocrinology, May 2019). Americans should not be afraid to include nuts and olive oil in their menus. After all, the research shows eating a healthful diet that includes these high-fat items won’t undermine your efforts to control your weight.
Mediterranean Diets for Heart Health:
The ability to control your weight was not the main thrust of the PREDIMED trial. The benefits of following a Mediterranean diet don’t have to come at the expense of keeping your figure. However, the investigators were primarily interested in learning whether the diet would help prevent heart attacks. The diets had fish or poultry rather than red meat and they had very little dairy products or sweet foods. The experimental diets had plenty of vegetables, fruits, whole grains and either nuts (a handful a day of walnuts, almonds or hazelnuts) or olive oil (4 tablespoons daily).
People following the Mediterranean diets had lower rates of heart attacks (Estruch et al, New England Journal of Medicine, June 21, 2018). These rates were 3.8 percent in the olive oil group, 3.4 percent in the nuts group and 4.4 percent in the control group. In addition, they enjoyed some protection from stroke, even if they had a genetic susceptibility (Corella et al, Diabetes Care, Aug., 2013).
Other Benefits of the Mediterranean Diet:
Data from the PREDIMED study have revealed many other benefits over the years. People following a Mediterranean diet had a lower likelihood of developing painful peripheral artery disease. This condition can make walking difficult (Ruiz-Canela et al, JAMA, Jan. 22/29, 2014). They had better blood sugar control (Babio et al, Canadian Medical Association Journal, Nov. 18, 2014). In addition, they were less likely to develop type 2 diabetes (Salas-Salvadó et al, Annals of Internal Medicine, Jan. 7, 2014). These volunteers were less likely to experience cognitive decline during the study (Martinez-Lapiscina et al, Journal of Neurology, Neurosurgery and Psychiatry, online June 3, 2013).
In addition, an analysis of data from about 7,200 of the participants revealed that those eating walnuts or using olive oil were almost 30 percent less likely to die during a six-year follow-up; those who consumed more fish were also protected from death due to heart disease (Sala-Vila et al, Journal of the American Heart Association, Jan. 26, 2016). That is a large amount of health benefit from a diet that can apparently help you control your weight!
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