Key to long term weight loss is as simple as more fat, fewer carbs

Zeroing in on long-term weight loss.


If you pay attention to the weight loss industry, you’ve been told over and over how easy it is to lose weight—just take this pill, follow that diet, or buy this piece of equipment, and everything will melt away in a flash. In fact, billions of dollars are spent each year on weight loss products and services and yet many people are still overweight.

Undoubtedly, losing weight is hard work but many people who have lost weight may agree that keeping it off can be an even greater challenge.

An absence of self-control or a couple of such a large number of dietary indulgences is frequently referred to as purposes behind regaining weight.

A new study by the Harvard Gazette suggests that the type of calories you consume may influence how likely you are to keep that weight off for the long term.

Through his study, scientists wanted to see if different levels of carbohydrates in the diet could prevent these metabolic changes from occurring, so that weight loss might stay off.

The emphasis on carbohydrates depended on the carbohydrate-insulin model of obesity, which holds that high insulin levels that come about because of eating a high glycemic load diet (i.e., highly processed carbohydrates like refined breads, crackers, cookies and sugars) cause energy from the food to be put away more effortlessly as fat, and may increase hunger and food cravings, lower energy consumption, and advance weight gain.

Scientists placed the study participants on a diet to lose about 12 percent of their starting weight to kickstart metabolic changes. The next phase randomly assigned the 164 participants who achieved this loss to one of three test groups:

  • High (60 percent) carbohydrate and low (20 percent) fat diet;
  • Moderate (40 percent) carbohydrate and (40 percent) fat diet;
  • Low (20 percent) carbohydrate and high (60 percent) fat diet.

The protein amount was the same in all groups, at 20 percent. Total calories were adjusted up or down in each participant to prevent any weight changes. All meals were provided to the participants during the weight-loss phase and throughout the 20-week test phase.

The types of foods in each diet group were designed to be as similar as possible, but varying in amounts: The high-carbohydrate group ate more whole grains, fruits, legumes, and low-fat dairy products, while the low-carbohydrate group ate more fat but eliminated all grains and some fruits and legumes.

After participants followed the diets for 20 weeks the researchers measured their total energy expenditure. They found that participants in all groups maintained their weight, and there was minimal difference in secondary measures, including physical activity and resting energy expenditure.

The outcomes suggest:

  • The low-carbohydrate group showed an increased energy expenditure, with a range of 209‒278 calories/day
  • The moderate-carbohydrate group showed a smaller increase in expenditure of about 100 calories compared with the high carbohydrate group.
  • The increased metabolic effect with the low-carbohydrate diet was most significant in people who had high insulin secretion at the start of the study, with an increased energy expenditure of 308‒478 calories/day.

Consuming a low-carb diet leads to a decreased hormone level responsible for increased appetite, ghrelin, and leptin. Thus, it leads to weight-loss maintenance. Leptin regulates energy balance and works to keep body weight stable. It typically counteracts ghrelin by sending signals to the brain to suppress appetite when the body has enough food.

David Ludwig, professor in the Department of Nutrition at the Harvard T.H. Chan School of Public Health said, “This study raises the possibility that a focus on restricting carbohydrates, rather than calories, may work better for long-term weight control.

Walter Willett, professor of epidemiology and nutrition at the Harvard Chan School, who was not involved in the study, noted that, “These findings from a carefully conducted investigation can help explain why low-fat/high-carbohydrate diets are not successful for most people and have failed to maintain weight loss in formal randomized trials that have lasted for one year or longer.”

The study is published in the November issue of BMJ.


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