Pregnancy Weight Gain: Its Implications for Understanding the Obesity Epidemic
Pregnancy weight gain may help us understand the nature of overweight and obesity.
Consider again our two competing hypotheses about what makes us fat and what can help us lose weight:
The dominant view is that "calories count." The Caloric Balance Hypothesis blames weight gain on the overconsumption or under-burning of calories.
The Lipophilia Hypothesis argues that changes in our body's fat stores manipulate our energy balance. When you gain weight, this makes you overeat or under exercise. When you lose weight, you're driven to take in fewer calories and / or burn off more of them.
So we have two hypotheses about pregnancy weight gain, both of which are plausible interpretations of the first law of thermodynamics. Caloric Balance tells us that women who become pregnant gain weight because they eat more calories than they "normally" do and/or because these women are less active. Somehow these "extra calories" get magically transformed into fat.
Lipophilia tells us that something more complicated is going on. It tells us that pregnancy induces hormonal changes in women. These hormonal changes alter the constitution of the fat tissue, which in turn drives a positive caloric balance. So the cravings women get when while pregnant ultimately stem from changes at the physiological level.
So what can the evidence tell us about pregnancy weight gain to resolve this debate?
1. Here is a fascinating article about pregnancy weight gain. First it tells us that the Caloric Balance Hypothesis must be true because its axiomatic. But then it goes on to tell us that sloth and gluttony don't cause all obesity. Instead, a variety of factors -- including pregnancy and other metabolic/ hormonal factors -- can influence our body weight. This second statement can only be true if the Lipophilia Hypothesis is correct.
The article begins:
"Whatever fad diet books tell you, the single most important factor effecting weight gain is the ratio of calories consumed to calories burned. Eat more than you work off, and you will gain weight."
After bowing in the direction of the Caloric Balance Hypothesis, however, the author then presents a slew of evidence that flies in the face of the hypothesis – evidence that factors other than changes in "Calories In" and "Calories Out" drive changes in weight.
2. Beyond the issue of pregnancy weight gain, we have to consider the pregnancy itself. Obviously, pregnant women add energy to their bodies in the form of a fetus. But can you really say that changes in "Calories In" and "Calories Out" "make" the fetus? Because if you believe in the Caloric Balance Hypothesis, you therefore must believe that our energy stores are solely and entirely manipulated by "Calories In" and "Calories Out." That's why we believe that overeating and under-exercising makes us fat and that eating less and exercising more makes us thin. But if you are going to make these claims, then you must tell people that the reason why pregnant women grow fetuses has nothing to do with hormones, genetics or anything else. It only has to do with calories. Somehow, when a pregnant woman establishes a positive caloric balance, she randomly turns those excess calories into baby.
Obviously, that explanation is absurd. A baby is obviously not just a garbage bag for excess calories. But if that's absurd, why is it okay to think of our fat tissue as a garbage bag for excess calories?
The paradox is only resolved when we look through the lens of Lipophilia. Changes in our body's energy stores drive changes in caloric balance. So when you change your body's energy stores – for instance, by growing a baby, or by accumulating excess fat in the fat tissue – this causes you to establish a positive caloric balance. Eating more calories is a result of pregnancy; it is not the cause of it. Similarly, eating more calories is a result of gaining fat; it is not the cause of it.
Once again, we see ample scientific and evidentiary justification for Lipophilia, and we see that Caloric Balance leads us into a nest of contradictions.