Are You Eating Enough Calories to Lose Weight with Hypothyroidism?

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While you'll run across an occasional expert who recommends extremely low-calorie diets for weight loss with hypothyroidism, the majority of experts believe that if you are on a diet that severely restricts your calorie intake, you may not be eating enough to maintain a healthy metabolism.

Calories and Metabolism

When it's operating efficiently, your body uses the food you eat for energy.

When you have burned off your food, your body turns to burning stored fat. If you restrict your caloric intake too much, however, your body bypasses this normal process and goes into a hoarding or starvation mode. When it's in that mode, your body holds onto your stored fat and instead turns to your muscles for energy. Not only does fat loss stall, but the reduction in your calorie-burning muscle mass can slow your metabolism. A slower metabolism translates to a reduction in your daily caloric requirement. In this way, cutting too many calories can actually lower your metabolism, and stall your weight loss efforts.  

How Many Calories Do You Actually Need?

Basically, you need enough calories to power your basic body functions and fuel any additional activity throughout the day. If your caloric intake is less than these requirements, over time, the calorie deficit should result in weight loss.

If your caloric intake is more than you need, the calorie excess results in weight gain. 

H​HS Guidelines: According to the Department of Health and Human Services, a general guideline is that sedentary men over 30 need from 2,000 to 2,400 calories a day, and active men require from 2,400 to 2,800 calories a day.

Sedentary women over 30 need 1,600 to 1,800 calories a day, and active women need from 2,000 to 2,200 calories per day. 

Body Weight RMR: Some experts say that you can roughly calculate your resting metabolic rate (RMR) by multiplying your body weight (in pounds) by 10. The total number of calories is considered a minimum that you should eat in order to lose weight. 

RMR Formula: You can also use a more complicated formula to calculate your caloric needs:

  1. Divide your current weight in pounds by 2.2, in order to convert your weight to kilograms.
  2. Multiply your weight in kilograms by 30. (30 is the number of calories you need per pound of body weight.)

So, if you are 160 pounds, you divide 160 by 2.2, which equals 73 kilograms. Multiply 73 kilograms by 30, which equals 2190, which would be how many calories you theoretically need to maintain your current weight of 160.

RMR Measuring: More accurate and personalized results are available by getting personalized metabolic testing of your RMR using devices such as BodySpec, and DexaFit. These tests are able to determine your specific RMR, and can confirm whether diet and exercise changes have had an impact on your metabolic rate.

Resting Metabolic Rate (RMR) Challenges

There are a number of factors that can skew these numbers, and not in your favor.


  • Hypothyroidism, especially if undertreated, may cause you to have a lower RMR than other people, even when you both have a similar body weight or activity level  
  • Lower muscle mass means that you will have a lower RMR than someone else, even at the same body weight. A muscular body burns more calories. 
  • Your RMR drops with age, as much as 2 percent each decade.
  • Previous or chronic dieting can lower your RMR. 

How Much Should You Eat? 

If the goal is to lose weight, how much should you eat? 

You need to eat enough to be able to lose weight without triggering the starvation mode, and lowering your RMR.

The solution is, according to many experts, minor calorie deficit, with slow weight loss, and aerobic and weight-bearing exercise at the same time. This combination approach appears to have the greatest chance of success without lowering your RMR. 

Experts on metabolism suggest that you maintain a calorie deficit of no more than 250 to 500 calories per day. 

One study published in the American Journal of Clinical Nutrition showed that exercising women on a moderate calorie-deficit diet lost 20 pounds over 4 months—a slow rate compared with many diets—with no decrease in RMR. 

A Word from Verywell

In addition to making sure that you are not eating too few calories and sabotaging your diet efforts, there are a few other things you can do to help raise your metabolism.

  • Build muscle: One thing you need to do is to focus on raising your metabolism, which can help raise your RMR. The key way? Incorporating muscle-building exercise into your fitness regimen and daily activity. Every pound of muscle you gain allows you to burn up to 50 more calories per day. That raises your RMR, and makes it easier to get that calorie deficit that results in weight loss. 
  • Include caffeine: Some studies show that daily caffeine intake can increase metabolism by 5 to 12 percent each day.
  • Switch to cold water: One research study showed that drinking 48 ounces of cold water daily can increase RMR by around about 50 calories daily, which could translate to 5 pounds of weight lost in a year. The increased metabolism is thought to be the result of the extra work it takes to warm up the water. 


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