Fat Reserves Equal Extra Nutrition On Board?

Reply turned post from My OB Said What?!:

“Well, you had a little extra nutrition on board when you got pregnant so you really don’t need to be gaining much weight.” – OB to mother who inquired about her low weight gain during her pregnancy; 

Comments like this represents another misperception that a lot of people have about nutrition and weight gain in women of size in pregnancy....that fat women are "over-nutritioned" and so have plenty of excess "nutrition" available for themselves or for a baby. 

This is one reason why some doctors champion the idea that fat women don't need to gain weight in pregnancy....they believe that because a fat woman is "over-nutritioned," she has plenty of nutrient and energy stores to draw from and therefore doesn't need the same amount of calories and/or nutrients that other women do.

For example, here's a quote from an article about doctors wanting to lower pregnancy weight gain guidelines:

Dr. Patrick Catalano of Case Western Reserve University in Cleveland said an obese woman has nutrients stored away and doesn’t need to gain weight to provide for the baby.

But does an obese woman really have "extra" nutrition stored away?  And is that really an adequate substitution for nutrients from fresh whole foods eaten during pregnancy?

The Context of the Original Post

The doc in the original post at My OB Said What?!? is probably just trying to reassure the mother that a lower weight gain is very common in women of size and not necessarily something to get very alarmed about. That's true. As long as the mother is not deliberately trying to restrict gain, her nutrition is good, and baby is growing well, things will probably be fine even with a low gain.

(As we've noted before, most women of size gain less in pregnancy than other women, and many gain very little in pregnancy even without restriction.  However, a policy of deliberate restriction to cause weight loss or little or no gain in women who would otherwise naturally gain may very well increase the risk of prematurity and too-small babies.)

The problem I have with his comment is the bit about "extra nutrition on board." He probably just meant it as a polite way to tell the mom she had extra fat reserves before pregnancy, so she didn't need to gain the same amount as women who don't already have those fat reserves. So I'll give this doc the benefit of the doubt and assume this was probably just his awkward way of saying it's not necessarily a problem if she gains less weight naturally.

But when many other doctors make this kind of comment (and I've seen it a number of times), what they really mean is that fat women can (and should) restrict intake significantly and baby will not be affected because of the fat mother's supposed extra reserves.

I strongly question the accuracy and wisdom of this.

Concerns With This Assumption

The doctors who favor strictly-limited caloric intake to restrict weight gains among women of size assume our fat reserves are basically "extra nutrition."  They reason that because we have supposedly have "extra nutrition," the baby will just take what it needs from mom and she therefore has little or no need for extra nutrition or calories.

There are several problems with restricting calories and assuming the baby will "get what it needs" from the reserves of the obese woman:

• It assumes that the mother has extra nutritional reserves just because she's got extra fat stores
• It assumes that getting nutrients from the mother's reserves is the same or at least as good as getting those nutrients directly from fresh food

Do Nutritional Reserves Really Substitute Adequately For Fresh Nutrient Intake?

Yes, the baby can get energy for growth from the mother's fat reserves, but that's NOT the same (or as valuable) as REAL NUTRITION from fresh food intake.

Doctors should be promoting a sensible diet and nutrients for mom and baby from fresh whole foods, not from the baby cannibalizing the mother's reserves.

Furthermore, if the mother's caloric intake is not sufficient for her energy needs, other things are sacrificed.  Anne Frye, midwife and author of Holistic Midwifery states:

If calories are insufficient, the body will burn available protein for energy instead. When protein is burned due to a lack of sufficient calories, less amino acids will be available for fetal growth and development, for albumin production to expand the blood volume, and to help with uterine muscle growth.

Doctors and midwives will often suggest a diet which provides plenty of protein (90-100g) but only 1500-2000 calories. Reasoning that the woman is eating a high protein diet, midwives may dismiss a woman’s diet as a causative factor when she develops toxemia [pre-eclampsia] or premature labor…Women must eat enough calories and protein from nutrient-rich sources to meet their particular requirements.

In a 2005 article,"Eating for two, gaining too much", Jacqueline Stenson quotes Dr. Michael Nageotte, then-president of the Society for Maternal-Fetal Medicine:

Though very low weight gain in some women may cause a baby to be underweight, even babies born to mothers who’ve endured famine have fared well, he says. “The fetus, being a very efficient parasite, if you will, is able to survive and get what it needs from the mother,” Nageotte says.

This is a dangerous assumption.  Although babies born during famine usually survive, they usually do so at a price. "Fetal origins" research clearly shows that many of them are at increased risk for diabetes, hypertension, insulin resistance, obesity, and heart disease later in life.  That is hardly faring "well."  Clearly, undernutrition in utero has serious potential consequences and should not be shrugged off so casually.

Furthermore, it is questionable whether the fetus is truly getting everything it needs from its mother.  Jeremy Appleton, ND, writes:

Evidence clearly contradicts the idea that a fetus can protect itself nutritionally when the mother is fasting or dieting. Although we know that a fetus can draw on maternal stores even when the mother is deficient, the extent to which this can occur is unknown. Data collected during the Dutch famine suggest that a malnourished mother protects her own body stores of nutrients at the expense of the fetus. During the famine, mothers lost proportionately less body weight (2% loss) than their fetuses (10% loss). Optimum fetal growth occurs only when the mother is able to gain a crucial amount of extra body weight during pregnancy. For this reason, pregnant women should not diet.

Naeye did a study that surveyed pregnancy outcome by weight gain over a group of over 50,000 women in 12 hospitals and found:

The fetus is exceptionally dependent on maternal nutritional reserves when mothers have very low weight gains…The quantity and balance of amino acids and other nutrients supplied from such maternal reserves may not be as favorable to the fetus as those largely deprived from dietary intake. Even large stores of depot fat do not seem to ensure an optimal outcome of pregnancy when weight gains are very low or mothers lose weight.

I think the assumption that babies will just take their nutrition from the mother's stores ─ and that this is just as good as getting it from dietary intake ─ has not been proven at all.  An "over-nutritioned" mother still needs fresh foods, adequate calories, adequate protein levels, and a wide variety of nutrients from dietary intake, just like any other mother.

Do Women of Size Really Have Extra Nutritional Reserves?

Furthermore, research shows that many people of size actually have nutritional deficits in things like iron, B-12, folate, and other areas.

For example, Schweiger 2010 recently found the following nutritional deficiencies in "morbidly obese" people just before they underwent weight loss surgery:

The prevalence of pre-operative nutritional deficiencies were: 35% for iron, 24% for folic acid, 24% for ferritin, 3.6% for vitamin B12, 2% for phosphorous, and 0.9% for calcium, Hb and MCV level was low in 19%...Patients with BMI [greater than or equal to] 50 kg/m(2) were at greater risk for low folic acid (OR = 14.57, 95% CI:1.4-151.34). 

Similarly, Aasheim 2008 found a number of nutritional deficiencies in "obese" patients:

Low concentrations of vitamin B-6, vitamin C, 25-hydroxyvitamin D, and vitamin E adjusted for lipids are prevalent in morbidly obese Norwegian patients seeking weight-loss treatment.

One author summed it up when he stated:

Though commonly considered a state of “overnutrition”, obesity has increasingly been recognized as a risk factor for several nutrient deficiencies, including lower levels of antioxidants and certain fat-soluble vitamins.

Doctors should not assume that if you are carrying "extra" weight, you automatically have plenty of extra nutrients available for baby. Many women of size actually do not.

Other Concerns

In addition, there are other concerns with placing mothers on restricted calorie diets during pregnancy:

• If the "obese" mother does not have good nutritional reserves, a restricted calorie diet makes it difficult to get the full range of nutrients needed for both the mother and the baby
• If the mothers' caloric intake is insufficent for her needs, fat stores will be burned and ketones will be spilled as a side effect, which may impair cognitive development of the fetus (as we've discussed before)

Therefore, I believe it is best to err on the side of caution and not assume that a fat mother has plenty of extra nutrients stored and can easily tolerate a restricted calorie diet.  I believe that fat mothers need the same or greater level of nutrients and similar (or only just slightly less, since we do not need to put down maternal fat stores) caloric intakes as other mothers.

Conclusion

While I think THIS doctor in THIS comment was probably just trying to find a polite way to reassure the mom about her lack of gain, many doctors have said something similar but meant it to justify restricting "obese" women's intakes in pregnancy.

Those doctors believe that the baby will draw any needed energy and nutrients from the mother's fat reserves and therefore it's fine to place the mother on highly restricted calorie diets in pregnancy.

THAT I have a problem with.

Although doctors think they are doing fat women a favor when they put them on restricted diets/weight gains, it is more likely that they are doing far more harm than good.