Why Diets Don’t Work

Woman staring at plate with one piece of broccoli on it looking frustrated resting her head on her hand.

Especially as an active woman over 40…

Allow me to clarify what I mean when I say diets don’t work.  Of course, the term diet can be used in the more general sense when talking about the way you eat.  For the purposes of this article, though, let’s talk about the trendy, often overly restrictive, lose-weight-quick plans that we try for a few weeks or months before quitting.

OK, now we’re on the same page, so let’s get back to the topic at-hand.  Diets don’t work.  If they did, the term “yo-yo dieting” wouldn’t exist.  You wouldn’t find yourself going on and off diets multiple times throughout your life.  You would find one that works for you and stick with it.

To be fair, when you were in your 20s and 30s, you may have been able to drop some weight when you went on a diet, and you might have even kept it off for a while.  Now that you’re over 40, though, you’re probably noticing that’s not the case anymore.  But why?

There are multiple reasons your body is either resistant to dieting or goes right back to your previous weight after you stop dieting.  Your body begins to change over 40, so you have to adjust your approach to weight management in a way that works with your changing hormones, not fighting them.  Let’s explore that some more, shall we?

Hormones, Hormones, Hormones

Even in your younger years, restrictive diets had negative impacts on your body’s hormones, specifically your reproductive hormones and thyroid hormone.  Now that you’re over 40, the implications are greater and more far-reaching. 

Let’s take a step back and talk about what hormones are.  Hormones are the link between the inner workings of your body and the outside world.  The foods and beverages you consume, the air you breathe, your environment, and the stresses you go through all trigger hormones to send signals throughout the body that cause specific reactions.

It should be noted that your body needs energy in order to produce hormones.

Different hormones have different functions, but they are all interrelated.  Here are a few specific hormones that play a big role in metabolism and weight maintenance.


Insulin is released in the body as a result of increased glucose, or sugar, in the blood.  Insulin’s primary role is to help glucose pass from the blood into cells, where it can be converted into energy.  Insulin is also an anabolic hormone, meaning it promotes storage of extra glucose and development of muscle.

Thyroid Hormone

Your thyroid is the master regulator of metabolism in the body.  Thyroid hormone not only sets your metabolic rate, but it also plays a role in digestion and muscle development.  Production of your thyroid hormone is negatively impacted by consuming less calories than you need.


Estrogen promotes fat storage to support reproduction, but it also protects against muscle and bone loss in women.  Estrogen levels begin to decline in women as the body prepares for menopause, usually sometime after 40.


Progesterone works with estrogen to support reproduction in women.  It also promotes storage of glucose as glycogen.  Like estrogen, progesterone levels begin to decline in women nearing menopause.


Often referred to as the “fight or flight” hormone, cortisol raises blood sugar, heart rate, and blood pressure, and just in general prepares the body to respond quickly to danger.  This response is good and necessary in short bursts.  However, when chronically elevated due to long-term stress, cortisol can lead to insulin resistance, decreased sensitivity to hunger and satiety signals, and disturbances in thyroid hormone, estrogen, and progesterone levels.

The Stress of Dieting

Let’s start with the mental and emotional stress of constantly having to be careful about what you eat.  Not being able to just enjoy a dinner out with your family or friends.  Regular weigh-ins and the inevitable emotional roller coaster when the numbers aren’t reflecting all the work you’ve put in.  These are all concerns that take a toll on your mental and, ultimately, physical health.

Additionally, forcing your body to function on less energy (i.e. calories) than it needs is stressful.  This stress is not the same as mental stress (though it can impact your mental health as well) and you might not even recognize it as stress.  It usually shows up in sneaky ways, like fatigue, stomach or intestinal issues, acne, headaches, or any host of other symptoms.

Effects of Diets on Metabolism

Calories = energy.  Unfortunately, though, that energy isn’t just ready to be used the second you eat.  It has to be transformed into a specific form of energy your body can use.  Metabolism is the process of breaking down and converting the foods you consume into that form of energy, ATP (adenosine triphosphate). 

When you consume less calories than your body needs to function at full capacity, your metabolism will decrease.  Basically, your body will slow down or stop certain “non-essential” bodily functions in order to conserve the limited amount of energy it has available. 

I should clarify that, when the body is determining which functions are essential, it is only looking at immediate survival, not long-term health and well-being.  Things like digestion and hormone production are impaired.  Brain function will slow.  Physical strength and endurance will suffer.

I mentioned above that calorie restriction impairs hormone production.  I should note that thyroid hormones are particularly sensitive to calorie restriction.  As noted, thyroid hormone regulates metabolism.  Low levels of thyroid hormone will negatively impact metabolism.  In women, this effect can occur within 4 days of calorie restriction, and takes 6 weeks or longer to recover.

To make matters worse, your body will start breaking down muscle proteins for energy.  Your muscle cells have a higher metabolic rate than other cells in your body due to a larger number of mitochondria, which is the part of the cell where most metabolism occurs. 

Other hormones that are particularly sensitive to calorie restriction include the female reproductive hormones, estrogen and progesterone.  Estrogen and progesterone work together and have multiple roles that aid in weight management, not the least of which is estrogen’s role in preserving muscle and progesterone’s role in supporting thyroid hormone.

Diets and Gut Health

Gut health refers to the balance of good bacteria and bad bacteria in your gut, or large intestine.  Simply put, the bacteria in your gut need food to live.  When you don’t consume enough calories to meet your needs, you aren’t consuming enough to keep the beneficial bacteria in your gut alive and reproducing. 

Studies have shown that healthy gut bacteria play a role in weight management.  While specific strains have had positive results in weight loss studies, a general overall positive balance of healthy bacteria is known to support the hormones and systems involved in maintaining healthy metabolism.        

Gut health can also refer to the health of the lining of your intestines.  Like the bacteria that live within your gut, the cells that make up the intestinal walls need energy to survive.  Restrictive diets can lead to breakdown of intestinal walls, which can lead to digestive issues and toxic particles escaping from the intestines into the bloodstream, which can lead to inflammation and stress (hello, cortisol!).

Restriction Isn’t Sustainable

If all the health concerns related to dieting haven’t convinced you to stop dieting yet, maybe this will be the kicker.  Restriction is not a sustainable lifestyle. 

Restrictive diets require a lot of work, planning, and skipping out on meals and social events.  It can be isolating.  And it requires a level of discipline and self-deprivation that most people are unable to maintain for a lifetime.  Even if you could make it a life-long habit, the decline in your metabolism would eventually stop any further weight loss and the weight would eventually creep back.

Weight Management Without Dieting

In summary, diets don’t work.  They aren’t sustainable long-term, and they can lead to stress and hormonal imbalances, loss of muscle, declines in metabolic rate, and damage to gut health.  As an active woman, your are putting greater demands on your body than your less active peers, so the negative impacts of restriction will show up more quickly and are often more severe.

That doesn’t mean weight loss isn’t possible, but there is no quick and easy fix.

Sustainable weight loss and long-term weight maintenance requires building life-long habits that support your body’s systems and boost metabolism.  This includes fueling your body with the right balance of nutrients, regular exercise that includes strength training, and stress management.

If you’re done with diets and want to learn more about healthy nutrition and wellness to support your active lifestyle, join me in my Facebook group.  Fit, Fearless, and Fed Women Run the World is a community of active women over 40 and I go Live to discuss nutrition and wellness topics regularly.  I hope to see you there!

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