Dr Roberts Answers Diet Questions from a Scientific Perspective: Part 1
This is the first of an educational series that talks about some common misperceptions about weight control, what you can realistically expect when you diet, and the science behind the real answers.
We have all seen the advertisements. A pound a day without hunger! 50 pounds achieved with these 3 simple steps! One weird trick! Eliminate this one harmful food to drop 6 clothing sizes without being on a ‘diet’!…
There is no limit to the lies that unscrupulous weight loss companies and fake diet docs are willing to try and get away with. And, sadly, because the Federal Trade Commission is overwhelmed and understaffed, there is usually no consequence to making these false claims, except that they confuse and discourage sensible people who want to lose weight and are willing to do what is necessary.
How much weight can I lose each week?
Those of you who studied physics in school may remember the First Law of Thermodynamics, which states that energy cannot be created or destroyed, only transferred from one form to another. When applied to weight loss, this means you cannot lose more calories from your body fat than the calorie requirements of your whole body.
So lets say that you are a person who usually requires 1500 calories a day to maintain weight. If you completely stopped eating for a week and maintained your activity at normal levels, so that all those 1500 calories your body needs were pulled out of your body fat, your body fat would decrease by… just 2.5 pounds each week. Of course, fasting for a week would be incredibly dangerous and something you should never do, but the point of this calculation is to demonstrate that body fat loss cannot be anything other than slow — compared to what unscrupulous weight loss companies promise.
To continue this thought experiment, although you would only lose 2.5 pounds of fat with your 7-day fast, you would lose a lot more weight — probably 10 pounds or so — because you would lose water, muscle and carbohydrate along with the fat. However, water and carbohydrate losses are temporary, and come right back on when you stop fasting, and muscle loss is dangerous, looks terrible, and hurts you in the long run by lowering your metabolism. ‘Fast’ weight loss is never sustainable. People wish for fast weight loss because they assume dieting is painful, and they want to get it over with as quickly as possible — like ripping off a bandage. But if weight loss can be accomplished without hunger or suffering — if it can be made enjoyable and sustainable, then you remove the need for extreme measures and can do it in a more healthful way.
What happens when I hit a diet plateau? Will I never lose as much weight as I want to?
Which leads us to the next question, which is how much weight you can lose totally? In a nutshell, that depends on how long you keep at it. My research at Tufts University has shown that “diet plateaus” are almost always caused by hidden calories creeping in, which is important to know because it means that you can almost always avoid weight loss plateaus by carefully sticking to your plan. If you are in an iDiet® group, this is something we help our iDiet participants to fine-tune.
How do I keep from regaining the weight I lost?
Although metabolism does fall after weight loss, the decrease is not large, and in fact is nearly proportional to weight loss — so for example if you lose 10% of your starting weight, you will then need eat about 10% fewer calories to maintain that smaller body. At iDiet we consider retraining your brain to like healthy food to be the key for sustainable weight loss, because if you genuinely enjoy healthy eating, it is easier to avoid sliding back into bad old habits and overeating again. Weighing yourself daily is another important strategy, so that if holidays, vacations and other life challenges start to cause backsliding, you can catch the problem quickly and get back on the wagon with a week or two by returning to your weight loss plan.
With best wishes,
Susan B Roberts, PhD
Coming up next week… are metabolism boosters real, and how can I lose weight in the places I want?
Choose the program that’s right for you.