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Lose weight with Calorie restriction? Not so simple.

Updated: May 19, 2022

Let's talk about one of the most common themes I hear in clinic: I am eating less calories, but I am not losing weight.

Sounds familiar?

How many times have you started calorie counting with some short term results only to regain your weight, and sometimes even more. And let's face it, calorie restricting may not be a pleasant experience if you are trying to lose a lot of weight. But there is also some science as to why you may have failed.

It turns out eating less calories ALONE will not necessarily lead to weight loss. Theoretically, it takes 3500 calories to lose 1 pound. So, the saying goes that if you have a caloric deficit of 500 per day you should lose one pound per week (500 calories x 7 days). But research and experience has shown this to be a flawed assumption. Let me demonstrate with one simple explanation: let's just look at yours truly. I weight 170 pounds. If I start a low calorie diet today and lose one pound per week, I simply cease to exist as a physical object after about 170 weeks. Even the starving poor who have much more significant caloric deficits don't cease to exist. So, the assumption that just by eating less calories you will lose weight is not necessarily correct.

Now, lets look at it from a more physiologic stand point: human and animal studies have shown that our body is very sensitive to any changes in caloric intake or energy expenditure; if we decrease our caloric intake, the body responds by increasing appetite and decreasing energy expenditure to bring us back to baseline. Evolutionary we have adopted to maintain our current weight. This s referred to as homeostasis, meaning that any change in our body leads to compensatory pathways to reverse the change and bring our body to its baseline. Homeostasis is in fact the main driving force for many biological processes in our body and is not limited to weight. So, whatever your current starting weight, your body sees that as normal. If you suddenly decrease your food intake you may lose a few pounds initially, but your brain sees this as a deviation from normal, a strong set of hormones that control your appetite, basal metabolic rate and digestion kick in to bring you back to your initial weight. Your appetite increases, hunger increases and energy expenditure decreases. This is why most diets with rapid weight loss fail. You may lose a fe quick pounds, but most likely you will regain it all back. Here is one study for the nerdy ones:

In a randomized study D. Polidori et al. used a medication that lowers blood glucose to see what happens with weight and energy. After 52 weeks, in subjects that received placebo (no active medication) there was no change in measured appetite (food intake) or energy expenditure. In those who received the drug (lower calories), there was a drop in daily energy intake (95kcal per kg lost weight) and drop in energy expenditure (25kcal per Kg lost weight). More importantly, there was no significant weight changes among the two groups by the end. Conclusion: a drop in caloric intake lead to compensatory mechanisms to bring the net energy back to baseline by increasing food intake and decreasing energy expenditure.

Now, there are also numerous studies and diet programs that show caloric restriction does lead to weight loss. But most of these studies are short term. Perhaps one of the best studies on long term effect of weight loss has come from the famous Biggest Loser Reality TV show. As you may remember, in this show over weight participants competed for the biggest weight loss through very restrictive caloric intake and exercise. However, 6 years after, participants had regained close to 70% of their initial weight (in fact only one participant has been able to maintain his complete weight loss). So, how to make sense of it all?

Here is the short answer: if you only restrict your caloric intake, or only exercise, you may lose a few short term pounds, but your body will adjust and brings you back to where you started. So, simply restricting calories does not work. However, if you combine your caloric restriction with exercise, physical activity and high quality food, then you will see gradual and permanent weight loss.

And how much do you need to restrict? This is up for debate. But from my own clinical experience, I have learned that calorie counting for long term does not work and just adds more anxiety to eating. Significant calorie restriction while exercising can also cause stress, anxiety and irritability. If you eat appropriate portions while physically active, your metabolism improves and you will gradually lose weight. So, I only recommend calorie counting as a starting point for a couple of weeks; this is only meant for you to realize your appropriate portion size (since most of us are accustomed to big portions). Once you get a hang of your portion size, I actually discourage you from calorie counting. Rather you should emphasize on eating high quality carbohydrates, fats and proteins and minimal snacking. If you are eating appropriate portion size, high quality food, exercising at least 5 days a week and maintaining daily activity, you will gradually start to lose weight. As an overweight person with elevated blood sugars who lost 30 pounds more than 10 years ago and has remained thin and fit, I can assure you this will work. I have also seen it work in numerous patients. So to summarize:

  1. start eating high quality carbs, fats and protein.

  2. eliminate snacking.

  3. short duration calorie count to regain appropriate portion size.

  4. exercise 5 days a week

  5. maintain physical activity every day

I will talk about how to exercise and remain physically active in the next blog.

One last word about calorie counting. Eating, exercising and being physically active should be a fun and enjoyable experience, so look at it as a lifestyle change and not an accounting chore of recording food and counting calories. As for me, I have learned to enjoy cooking, going to farmers market on Saturdays and being part of the triathlon community; my healthy life has become a lifestyle change, not a source of stress. Find yours.


1) How Strongly Does Appetite Counter Weight Loss? Quantification of the Feedback Control of Human Energy Intake

2) Kevin Hall Obesity Sept 2021.

3) Physical Activity Patterns in the National Weight Control Registry

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