What Research Says About Dieting

I am an enthusiastic subscriber to NutritionFacts.org videos. As I’ve mentioned in a prior post, Dr. Greger and his team wade through thousands of scientific articles annually to keep the general public informed on the latest findings on nutrition. And they do it for free!

On Friday, I joined thousands of other folks for a NutritionFacts.org webinar re: dieting and the efficacy of fasting. Dr. Greger shared previews of videos that will be posted on the site over the next several months in support of his upcoming book, How Not to Diet. Here are just a few of the things that I learned.

piggy scaleA long-standing maxim regarding weight loss goes something like this: 1 pound of fat is equivalent to 3500 calories. Therefore, if you want the bathroom scale to register one less pound, simply reduce your daily caloric intake by 500 calories for 7 days. Trouble is, the body doesn’t quite work that way.

The body’s “math” says that weight loss is a function of CALORIES IN (i.e., what you eat) minus CALORIES OUT (i.e., what the body has to burn to keep you alive). A heavy person’s body at rest will burn more calories than a thin person’s body at rest because there’s a lot more tissue and blood vessels to maintain. As a heavy person loses weight, it takes increased caloric restriction over time to sustain the same rate of weight loss. But that’s not all…

Our bodies have been hard-wired over millions of years to defend against scarcity. When they confront caloric restriction, they’ll respond by lowering their metabolic rates to ensure survival. They’ll also amp up the hunger sensation to get us to forage for food. As such, it takes that much more willpower to stay the course!

Folks often complain that their diets stall after about 6 months. Both factors noted above contribute to that result. But there’s an insidious little factor that slips beneath our level of awareness. Studies show that most dieters inadvertently start eating more food over time. At the 6-month mark, they may feel as though they’re still eating 500-600 fewer calories every day, but they’re actually only eating 200 fewer. The hunger drive gets the better of them and distorts their perceptions.

Fasting has become a popular tool for weight loss due to its potential for rapid results. But the research doesn’t bode well for this approach. During fasts, the body cannibalizes itself, using lean muscle mass to create fuel. Moreover, fasting for a week or two can interfere with the loss of body fat long term. Fasting also deprives the body of essential vitamins and minerals. That deficit can result in serious (even fatal!) consequences. Breaking fast is also dangerous if not pursued intelligently. The body can’t turn up its digestive functions on a dime. Anyone considering this technique for weight loss should only do so under medical supervision with folks who know what they’re doing!

Folks who opt to lose body fat through liposuction may lower their body fat composition but do not reap the benefits of improved health. That procedure simply removes subcutaneous fat. It’s the visceral fat – i.e., the stuff that surrounds our vital organs – that wreaks havoc on our systems, leading to hypertension, arteriosclerosis, insulin resistance, etc. So while clothes may fit better, the newly thinner person is not a healthier person.

Sustained weight loss requires a consistent deficit of 300-500 calories daily. To meet this requirement, Dr. Greger tell us not to eat less food of the kinds you’ve always eaten; rather, eat better food. You can lower the caloric density of meals and keep hunger in check by pursuing a whole food plant-based diet. You also do yourself a big favor by consuming your calories earlier in the day. He tells us to eat breakfast like a king (queen), lunch like a prince (princess), and dinner like a pauper.

Exercise needs to factor into the mix. Surprisingly, it doesn’t have anywhere near the impact of calorie restriction on weight loss. BUT exercise improves muscle mass, and resistance training prevents bone loss that can occur with calorie restriction. The research also suggests that it’s best to exercise first thing in the morning before eating.

Finally, our bodies like to have a daily fast of ~12 hours in duration. So, set aside a 12-hour window for eating (e.g., 7:30am to 7:30pm) and drink water and herbal tea during the other hours. That practice alone supports weight management as we tend to eat less healthy foods at day’s end.

If you’d like to find out the optimal number of calories to drop for weight loss based on your current weight and level of activity, check out the NIH Body Weight Planner.