A small but eye-opening study published in the American Journal of Clinical Nutrition, found that overweight and obese people who increased their fat intake and lowered the number of refined carbohydrates had greater improvements in their cardiovascular disease risk factors than people following a similar diet lower in fat and higher in carbohydrates.
For the past 50 years, nutrition experts and physicians have strongly advised patients to avoid artery-clogging saturated fats, such as those found in red meat and butter, fearing that doing so would increase the risk of heart disease. This philosophy was based on evidence from clinical trials showing that saturated fats increase LDL “bad” cholesterol, a major risk factor for cardiovascular disease.
The problem though is that when people reduce saturated fat intake, they often replace it by eating more refined carbohydrates, which does not help reduce heart disease risk and could lead to other adverse effects such as increasing triglyceride levels, lowering HDL or “good” cholesterol, and increasing risk factors related to insulin resistance, thus raising the risk of type 2 diabetes.
But researchers with this new study hypothesized that following a low-carbohydrate diet by reducing refined carbohydrate foods (cake, cookies, pastries, pies, white bread, white, rice, etc.) would improve lipoprotein insulin resistance, a marker associated with type 2 diabetes and premature coronary heart disease.
The study which spanned five months chose 164 overweight and obese adult participants, mostly women, who took part in two phases. The first phase involved placing each participant on a strict, low-calorie diet helping lower body weight by about 12 percent. The second phase involved assigning each participant to follow one of three diets in which 20 percent, 40 percent, or 60 percent of their calories came from carbohydrates. Protein content was kept constant at 20 percent of calories in each diet, with the remaining calories coming from fat. All participants were provided fully prepared meals throughout the study to improve dietary adherence.
As a comparison, the average American carbohydrate intake is around 50 percent of their calories with most of it coming from highly refined and processed foods like sugary beverages, snack foods like crackers, chips, and cookies. While the participants in this study were on a lower-carbohydrate diet than the average American, it was not considered a ketogenic or “keto” diet which restricts carbohydrates to less than 10 percent of daily calories which forces the body to burn fat instead of carbohydrates. The study participants also did not eat unlimited amounts of food high in saturated fat such as bacon, butter, and whole milk.
For each of the diet groups with the study, the researchers provided healthy meals that included foods such as vegetable omelets, chicken burritos with black beans, toasted lentil salads, and grilled salmon. However, participants in the high-carbohydrate group received foods such as whole wheat bread, brown rice, multigrain English muffins, skim milk, and vanilla yogurt. The low-carbohydrate group did not include the bread, rice or sugary yogurts but instead had meals with high-fat foods such as whole milk, cream, butter, guacamole, olive oil, almonds, peanuts, pecans, and soft cheeses.
The surprising finding from this study was that participants in the low-carbohydrate, higher saturated fat group in which 21 percent of their daily calories came from saturate fat, did not experience an increase in their cholesterol levels. The amount of 21 percent of calories coming from saturated fat is twice the amount of what the Dietary Guidelines for Americans recommend. The LDL cholesterol stayed about the same for these participants which were the same as those who followed the high-carb diet with only 7 percent of their calories coming from saturated fat.
Two important findings this study showed further pointing towards recommending diets higher in saturated fats and lower in refined carbohydrates, was one, the low-carbohydrate group had a 15 percent reduction in their levels of lipoprotein, a fatty particle in the blood strongly linked to increasing heart disease and strokes.
The second important finding was the participants on the low-carbohydrate diet had a drop of 15 percent in their lipoprotein insulin resistance scores, or LPIR, a measure of insulin resistance while participants on the high-carbohydrate diet had their LPIR score increase by 10 percent. Studies have found that people with high LPIR scores are more likely to develop diabetes.
The low-carbohydrate group of participants also experienced other improvements as well. They had reductions in their triglycerides levels, a type of blood fat that can increase heart attacks and strokes; and their level of adiponectin, a hormone that helps lower inflammation making cells more sensitive to the uptake of insulin, increased. High levels of inflammation throughout the body are linked to the development of age-related illnesses such as heart disease and diabetes.
From the results of this study, the message is loud and clear – eliminate highly processed and sugary foods while still leaving room for “high quality” carbohydrates such as whole fruits and vegetables, beans, legumes, and other plants, can be quite helpful in reducing the risk for heart disease, type 2 diabetes, and other metabolic conditions associated with growing older.
The other message is that “healthy” amounts of quality saturated fats, such as whole milk, small portions of lean red meat, avocados, butter, nuts, olive oil, fatty fish, and seeds, can be part of a healthy diet as long as they are eaten in moderation.
So, replace highly refined and processed carbohydrate foods with healthy whole foods and fat, including saturated fat, to help achieve better metabolic and cardiovascular health benefits.