When we decide to "get healthy," losing weight is usually at the top of our "to do" list. And while exercise definitely helps, our eating habits usually need an overhaul if we plan to shed pounds. So the search is on for the "right" weight-loss plan. We research diets on the internet, read magazines from the grocery store checkout line, and talk with family, friends, or health professionals to determine the best method to reduce excess body weight. For some, comparing the weight-loss options can be almost as exciting as watching the numbers go down on the bathroom scale. Once the diet begins and we start seeing the changes on the outside of our body, we anticipate that improvements are taking place on the inside. Biomarkers for cardiovascular health such as cholesterol levels and triglycerides should all go down as our weight drops. But is this assumption true? Does it matter what eating style we choose so long as we lose weight? Will all weight loss lead to improved cardiovascular health? Let's look at what the science says.
In a longitudinal study published in Preventive Cardiology, researchers started with a basic premise: "Any dietary program that reduces the number of calories a person eats to fewer than what he or she needs will result in weight loss." They recognized that weight loss diets primarily juggle the percentage of calories coming from the three macronutrients. The majority of diets fall into one of three basic categories:
1) high-fat, high-protein, low-carbohydrate
2) moderate-fat, moderate-protein, high-carbohydrate
3) low-fat, moderate-protein, high-carbohydrate
Since weight loss could occur on any of these arrangements of nutrients, the researchers wanted to determine the effects of each diet on not only weight loss over the course of a year, but also on certain biomarkers for cardiovascular disease. They recruited 53 women and 47 men between the ages of 23 - 67 who had no other medical conditions beyond the need for weight loss. The participants generally weighed close to or well over 200 pounds. An hour of exercise three to five times a week was encouraged, and most reported exercising at least three times a week for an average of 30 minutes; intensity varied by individual. Weight was measured and blood was drawn every four months. Participants were randomly assigned to one of four dietary styles based on their stated preferences. There was no statistical difference between the groups for age or sex.
High-fat (HF) Diet: 55-65% of calories from fat; 25-30% protein; the rest from carbohydrates.
Moderate Fat (MF) Diet: 20-30% of calories from fat; 10-20% protein; 60% carbohydrates. (This diet is closest to the typical American diet which is 35% fat, 15% protein, and 50% carbohydrates.)
Moderate Fat, Calorie Controlled (MF-CC) Diet: 15% of calories from fat in a 2:1 ratio of nonsaturated to saturated fats with no more than 5g of saturated fat per day; 15% protein; 70% carbohydrates (emphasis on complex vs. simple carbs).
Low-fat (LF) Diet: 10% of calories from fat; 15% protein; 75% carbohydrates (emphasis on complex vs. simple carbs). The diet was 100% plant based. Participants were given a multivitamin.
Percentage of Weight Loss After 12 Months on Diet
(HF) = 13.7% (ate until satiated)
(MF) = 2.6% (ate 10-12 calories per pound per day)
(MF-CC) = 12.6% (asked to eat 350-500 calories less per day than required to maintain body weight)
(LF) = 18.4% (ate until satiated)
Participants following the HF, MF-CC, and LF diets all ate 1600 or fewer calories per day.
Effect on Cholesterol and Triglycerides After 12 Months on Diet
(HF) = 4.3% increase in total cholesterol; 6.0% increase in LDL "bad" cholesterol; 5.8% decrease in HDL "good" cholesterol; 9.8% increase in ratio of total cholesterol to HDL
(MF) = 5% reduction in total cholesterol; 6.1% reduction in LDL "bad" cholesterol;1.5% decrease in HDL "good" cholesterol; 5.3% decrease in ratio of total cholesterol to HDL
(MF-CC) = 30.4% reduction in total cholesterol; 38.8% reduction in LDL cholesterol; 3.6% increase in HDL "good" cholesterol; 34.7% decrease in ratio of total cholesterol to HDL
(LF) = 39.1% reduction in total cholesterol; 52.0% reduction in LDL cholesterol; 9.0% increase in HDL "good" cholesterol; 45.8% decrease in ratio of total cholesterol to HDL
Effect on Triglycerides and Homocysteine Levels After 12 Months on Diet
(HF) = 5.5% increase in triglycerides; 12.4% increase in homocysteine
(MF) = 1.0% increase in triglycerides; 9.7% increase in homocysteine
(MF-CC) = 36.9% decrease in triglycerides; 14.6% decrease in homocysteine
(LF) = 37.3% decrease in triglycerides; 13.6% decrease in homocysteine
Triglycerides is the level of circulating fat in the bloodstream. Homocysteine is an amino acid which is linked to increased risk of heart attack and stroke when present in higher levels.
Are All Diets Equally Effective?
According to this study, there is more than one way to be successful at weight loss. Participants lost a significant percentage of excess weight on the high-fat diet, the calorie-controlled moderate-fat diet, and the low-fat plant-based diet. But as a physician, I like this study because it lets us watch the effects of a chosen diet on the risk factors for disease over the course of a year. If you review the full study, which can be found through Starch-Smart.com, you can see that four months into the diet, the high-fat participants showed lowered triglycerides and a lowered ratio of total cholesterol to HDL cholesterol. The changes were modest compared to some of the other diets, but the numbers in those two categories were moving in the right direction. Many people might feel they were having "success" and would assume that the trend would continue. It didn't. Eight months into the study when other diet groups were recording significantly improved biomarkers, the high-fat group was beginning to show the longer-term effects of their dietary choices.
When I work with obese patients to help them lose weight, I not only want to see them experience the energy and freedom of movement that weight loss brings, but I also want to see them maximize their available health and longevity. My target for my patients is to get their total cholesterol into the 'safe zone,' which means a total cholesterol below 150. Caldwell Esselstyn, Jr., MD, referring to the Framingham Heart Study, says that 150 is the number that makes us heart-attack proof. Looking at the biomarkers of the participants in this study, I am alarmed that after a year on a high-fat, high-protein, low-carb diet (similar to Atkins or Paleo diets), all of the biomarkers for those participants had moved in the wrong direction. People looked better on the outside, but were "sicker" on the inside. Their risks of a heart attack or stroke had gone up. As an emergency physician, board certified by the ABEM, I can tell you that unfortunately, the first symptom of heart disease for some people is a heart attack. And not everyone lives through their first heart attack. That's why the numbers associated with the high-fat diet concern me. The participants' weight went down, but with a diet like this, people can die while looking pretty good. By contrast, I'm impressed with the numbers put up by the low-fat plant eaters. Everything was moving in the right direction from the beginning, and the final numbers were the best-of-class in nearly all categories.
I can tell you from experience here in my office that when patients begin eating low-fat plant foods, leaving off the oil and enjoying all the fabulous textures, colors, and flavors plants offer, they, too, often begin seeing their numbers move in the right direction. Weight goes down, cholesterol drops (sometimes dramatically), blood pressure begins to normalize (often very quickly), and diabetes medications can often be reduced or eliminated. I love helping my patients find new health and the promise of added years simply by filling their plates with low-fat whole plant foods. It's the most effective diet I've found to restore health. And with this study, we've seen the science that proves it.
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