• Allison Fahrenbach

Undereating & Weight Gain in Women

I have posted on social media outlets before about the dangers of chronic under-eating. And while under-eating can negatively affect both men and women, in women, I feel that the impact of undereating is magnified.

Women simply aren't wired to handle extreme caloric deficits with the same efficiency that men are.

I also feel that women, more so than men, are prone to falling into the habit of CONSTANTLY being in some sort of caloric deficit. Ironically enough, many of these same women are complaining about how they can't lose weight or bodyfat, or how their body never changes, or how their physique never looks as they'd like it to.

Unfortunately, mainstream information on weight loss leads you to believe that the body is a machine and all it takes to change how you look is simple math; calories in versus calories out. Eat less then you burn and voila- weight loss. And when weight loss stalls, just cut calories again.

But honestly- think about it- if it was THAT simple, we'd all be lean.

The body is more complex then that.

So while it may seem counter intuitive to say that chronic undereating can actually cause weight gain, the truth is, that it can.

Which is what I want to discuss in this post.

While calories in vs calories out is "true" to an extent, you can't just expect to input "x"calories and miraculously see "x" response. The body is an adaptive organism, hard wired for survival and as you make changes to your diet and training, your body in turn, makes changes of its own. It upregulates certain hormones, downregulates others, and makes a series of metabolic adaptations ALL of which affect your ability to lose weight.

Slight calorie deficits and tweaks can help lead to sustainable weight loss, but it's been my experience that dramatic or extreme deficits **utilized for long periods of time usually cause the body to adjust thyroid, adrenal and sex hormones to the point at which the negative impact is just too great.

**NOTE: Short term dramatic calorie cuts are NOT the same as chronically being underfed

And these changes are magnified in women, mostly because of the impact severe under-eating has on TWO THINGS:

  1. The thyroid

  2. Cortisol production.

Under-eating does two things: it downregulates thyroid and upregulates cortisol. This lethal combination makes it VERY hard to gain control of your weight.


Chronically elevated cortisol (stress hormone) leads to weight gain via leptin and insulin resistance and chronic under-eating causes a down regulation of T3 (active thyroid hormone).

This can lead to a condition called euthyroid sick syndrome, where T3 is low, reverse T3 is high, and TSH and T4 are often normal.

This means your body develops symptoms of hypothyroidism without necessarily showing any change in typical thyroid function markers. Basically, your bloodwork wouldn't indicate that you have hypothyroidism but you are still going to display symptoms of it, some of which are:

1) Inability to lose weight (as I mentioned above, due to the combination of increased cortisol output and downregulated thyroid function)

2) Constipation or impaired digestion. This is a very common symptom of hypothyroidism, as active thyroid hormone helps stimulate peristalsis in the gut, keeping digestion humming along smoothly. When T3 drops, gut motility slows, and this can lead to chronic constipation.

3) Sleeplessness or insomnia. Inappropriate calorie and carb intake can cause insomnia or difficulty sleeping. As blood sugar drops overnight, the liver releases stored glucose to keep blood sugar steady. But if you're under-eating, and glycogen stores are chronically depleted, the body has to release stress hormones like cortisol and adrenaline to fuel a process called gluconeogenesis,which creates glucose. If these hormones are high enough they can wake you in the middle of the night and/or prevent you from falling asleep. And lack of sleep, particularly over time, leads to weight management difficulties, mostly because of the elevated levels of cortisol in the body which impede weight loss or fat loss and can even cause weight gain.

I'm not saying that women can't handle a caloric deficit (they can) and yes, a calorie cut is likely warranted when weight loss is of concern (so don't think just because your coach or trainer has you cutting calories you're doing it wrong).... BUT if you've been GROSSLY under-eating, as many women do, for months, even years on end, and are struggling to lose weight or are maybe even gaining weight, consider this post. You may want to re-evaluate your approach.

Often times, as a coach, when I work with a woman who is coming to me with A history of undereating, I do two things. The first is that I begin to dial back on a woman's activity level (reduce her cardio or training) and secondly, I gradually coax her to eat more. When I do this, several things happen:

1) Digestion improves, and thus weight loss improves (less stomach volume = drop on the scale)

2) Sleep improves, and thus weight loss improves (lowered cortisol = drop on the scale)

3) Energy improves, and thus training improves, so weight loss improves (more intense training = drop on the scale)

4) Her body looks better- She tends to look LESS skinny/soft look and MORE athletic, lean, and muscular. This is because being under-fed leads to deflated muscles and typically places the body in a catabolic or muscle wasting state. This shift in body composition also occurs as a result of lowered cortisol. Cortisol tends to cause adipose tissue accumulation in the abs, low back, upper thighs and buttocks, and therefore, when cortisol comes down, these areas tend to see visual improvement.

I feel more women need to realize that the answer to weight loss isn't always to just log hours of cardio and continue to reduce or restrict your caloric intake. it's important to know that chronic, long term under-eating can hurt your health and body composition the same way over-eating can.

By constantly undereating you are placing yourself in a position to deal with some serious health issues. In my opinion, health is never worth the compromise just to be one jean size smaller or hit some weight loss number you "think" you need to be.

Health can, and should ALWAYS come first.

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