With the obesity epidemic at an all-time high in the US — close to 70% of Americans are overweight or obese — many people could benefit from losing weight. However, for numerous reasons, weight loss is challenging. In addition, some people are tempted to choose the “diet of the month” or a plan that they have read about online or heard about from friends and family. Unfortunately, these diets are oftentimes not the most nutritious, and even with some weight loss, may not ultimately improve health.
So, is there any benefit from improving the quality of one’s diet without weight loss? The answer is YES. Three randomized clinical trials (the gold standard in nutrition research) have shown that by improving what you eat, you can improve cardiovascular risk factors, such as high blood pressure, LDL (bad) cholesterol, and triglycerides, and improve your health.
Examining the evidence
One study examined the effect of the DASH (Dietary Approaches to Stop Hypertension) Diet on blood pressure. The researchers recruited 460 overweight and obese adults with borderline high blood pressure. They provided the participants with food according to DASH diet guidelines. The DASH diet is defined as: low in saturated fat and dietary cholesterol; rich in potassium, magnesium, calcium, and fiber; emphasizing fruits, vegetables, whole grains, and low-fat dairy products; including fish, poultry, nuts, and seeds; and limiting red meat, sweets, and sugary beverages. To prevent any effect from weight changes on the results, researchers regulated calories to prevent weight gain or weight loss. At the end of the 11-week study, the participants’ blood pressure was significantly reduced compared to their baseline blood pressure.
The second study looked at the already very healthy DASH diet and then added sodium limits. Study participants on the DASH diet who were assigned to the lowest sodium limit (1,500 milligrams per day) experienced drops in blood pressure similar to what a blood pressure medication would achieve.
The third trial examined whether changing a few components of the original DASH diet could result in even greater improvement in risk factors. This study, called OMNI Heart (Optimal Macronutrient Intake to Prevent Heart Disease) examined 164 overweight and obese adults with prehypertension or Stage 1 hypertension, and replaced some of the carbohydrates in the DASH diet with either healthy protein (from fish, nuts, beans, and legumes) or unsaturated fats (from olive oil, nuts, avocado, and nut butters). Again calories were kept neutral to avoid weight gain or loss. Results showed that substituting healthy protein or healthy fats for some of the carbohydrate lowered LDL (bad) cholesterol, blood pressure, and triglycerides even further than the DASH diet alone.