Low-Carbohydrate Diets and LOSING Weight while Pregnant

Since my wife is pregnant, I have been thinking more about maternal and fetal issues and how they relate to nutrition, fuel partitioning, and weight management. She is thrilled for me.

One question I had while going for a walk was: Is it dangerous for a woman to lose weight during pregnancy? Dr. James Carlson has reported that he probably worked with thousands of mothers who lost weight during pregnancy on a low-carbohydrate diet and developed healthy babies while dropping as much as 50-60 pounds in the process.

The conventional wisdom holds that a mom shouldn't be losing weight while pregnant because there is an implicit assumption that the mother would be restricting calories; she would be semi-starving herself, therefore she would be starving the fetus, which would obviously be a problem, for both mother and fetus.

However, when you view it from the carbohydrate-hypothesis paradigm, low carbohydrate diets do not restrict calories, they do not restrict essential nutrients, and they generally improve the relative health of the mother, and therefore the baby as well.

When a mother is losing weight on a low-carbohydrate diet, while pregnant or not, she is not losing weight because she is eating less, she is eating less because she is losing weight.

For a non-pregnant woman, more fatty acids are liberated from adipose tissue and she literally has more energy circulating to provide endogenous fuel to her cells and, if she 'overeats,' for increased expenditure through both exercise (“activity thermogenesis”) and non-exercise activity thermogenesis (NEAT). She doesn't eat as much energy because her body is now providing more energy from her fat stores.

If higher levels of insulin drive more fat accumulation, lower levels of insulin help drive fat utilization. (It is worth noting that there is physiological insulin resistance that occurs during pregnancy. This will be covered in a subsequent post.)

For a pregnant woman losing weight on a low-carbohydrate diet, the same holds true as above, but in addition, she is also supplying energy to the baby. She eats less because she is losing weight through lipolysis, and now some of that fuel gets partitioned to the fetus as well. So long as she has ample fat tissue and is providing adequate energy and nutrients for her own needs, as well as her fetus, who cares how many calories she is eating?

A low-calorie, low-fat, low-cholesterol diet flies in the face of reason while pregnant. Keep in mind that this very same argument for pregnant women holds true for the population at large.

The fetus needs adequate energy, fat, and cholesterol for proper and healthy development.

All human beings require the same. To restrict calories, fat, or cholesterol is to restrict the organism from its physiologic needs. If one of these essential nutrients is being restricted, why wouldn’t we feel less than adequate?

For a woman with adequate adipose tissue, losing weight while pregnant is not dangerous, so long as the "weight", i.e., the energy, is being supplied to the fetus.

We're not violating the laws if thermodynamics here, we're transferring our energy to the fetus, and the result is that one system gets relatively smaller (the mother's fat tissue) and another system gets bigger (the fetus).

And for a non-pregnant woman on a low-carbohydrate diet, one fuel supply gets smaller (exogenous calories, i.e., food, i.e., "calories-in") while another fuel supply gets larger (endogenous calories, i.e., body fat, i.e, "calories-out").

We lose weight on a low-carbohydrate diet while we are in "energy balance" as the conventional wisdom portrays it. The conventional wisdom doesn't account for "calories-out" provided by our own energy stores in this context. But this is the fundamental driver of obesity and leanness. Expenditure is exceeding intake at the level of the fat tissue. Isn't that what we care about if we don’t want to be obese?

And for the fetus, does it grow because it takes in more energy or does it take in more energy because it’s growing? So long as we are supplying a metabolically healthy fetus with adequate nutrients, it will take what it needs for normal development. The fetus "eats more" because the fetus is developing and requires more energy.

We haven’t even begun to discuss the importance of breast milk, which also requires fuel to produce (breast milk is fuel, after all); and the rationale is for pregnant women to gain 10 pounds to provide a reserve to be utilized for breast milk. But if the pregnant mother is obese, for example, doesn’t she already have the maternal reserve?  

And what does "calories-in/calories-out" have to do with this fuel partitioning as well? Are we that naive to think there has to be a conscious, or behavioral, manipulation of caloric intake in order for us to gain the appropriate weight for breastfeeding as well as embryological and fetal development? 

Why are we this naive when it comes to obesity and leanness?