Diet during pregnancy

During pregnancy, many women look for ways to improve their diet. Weight gain during pregnancy is expected but within healthy limits. Fats contain the most calories per gram (9 calories per gram versus 4 calories per gram for carbs and protein) so dietary fats often get the most scrutiny. But there are dozens of kinds of fats to choose from. The array can be mind-boggling. Fortunately, scientists at the University of California (UC), Riverside, are conducting a series of tests that compare the pros and cons of various fats and oils. They find that some fats, such as soybean oil, are linked to more excess pounds than others.

Fats and Oils

Fats and oils are both fatty acids that the body requires for optimum health but too much of either can lead to undesirable added pounds, obesity, and medical complications that include diabetes, fatty liver disease, irritable bowel disease (IBD), and cardiovascular disease.

Fats are solid at room temperature; oils are liquid. The difference is the chemical structure of the fatty acid molecules but they both pack the same high-calorie punch. Overconsumption of either can lead to extra pounds.

Four Diets

The UC research team used mice in their study, which involved feeding four different groups of mice four different diets and then examining them for evidence of weight gain and other negative effects. The four diets in their most recent study contained 40% fat, which is what the average American human eats. All diets contained the same amount of food and the same number of calories.

The difference in diets was the type of fat or fructose each contained. Fructose is the main sugar ingredient in many sweetened beverages. As food and beverage manufacturers added more and more fructose to their products, the more and more pounds the average American gained.

The four diets under study involved:

  • Diet #1 — 36% coconut oil (a solid plant-based saturated fat) and 4% soybean oil (a liquid plant-based fat thought to be healthier than saturated fats). Saturated fats are most commonly associated with animal fats such as butter and lard and have been strongly associated with cardiovascular disease.
  • Diet #2 — 19% soybean oil and 21% coconut oil.
  • Diet #3 — the same fat composition as Diet #1 but with fructose added.
  • Diet #4 — the same as Diet #2 but with fructose added.

Four groups were fed one of these four diets for 16 weeks; another four groups were on these diets for 35 weeks.

Study Results

The results were varied but those on Diet #2 (soybean oil) seemed to suffer the most negative health consequences:

  • The mice on Diet #2 gained the most weight: 25% more than Diet #1 and 9% more than those on Diets #3 and #4.
  • Diet #2 produced larger fat deposits, symptoms of fatty liver disease, and insulin resistance. A human with these symptoms would be diagnosed with Metabolic Syndrome, a disorder that almost always signals the development of type 2 diabetes. Some mice in this group developed diabetes during the study.
  • Diet #4 produced less severe markers for metabolic disease but some mice developed symptoms of kidney disease and a high rate of prolapsed rectum, signaling inflammatory bowel disease. As the obesity rate in the US climbs, so does the rates of IBD cases.
  • The mice on Diet #4 gained 12% more weight than those on Diet #3.

Soybean Oil in the Food Supply

Soybean oil is a major ingredient in many processed foods, especially sauces, salad dressings, and sandwich spreads such as mayonnaise. For healthiest fat intake, read labels and avoid foods that list soybean oil as one of the first five ingredients. Most soybeans used in the mass-produced food supply come from genetically modified (GMO) sources.


  1. Nealon, Sean. "Soybean Oil Causes More Obesity Than Coconut Oil and Fructose." UCR | Today. Regents of the University of California, 22 July 2015. Web. 6 Aug. 2015.
  2. Deol, Poonamjot, et al. "Soybean Oil Is More Obesogenic and Diabetogenic than Coconut Oil and Fructose in Mouse: Potential Role for the Liver." PLOS | One. PLOS, 22 July 2015. Web. 6 Aug. 2015.
  3. "Healthy Cooking Oils Buyer's Guide." Million Hearts. Centers for Disease Control and Prevention / US Department of Health and Human Services, n.d. Web. 6 Aug. 2015.