Factors like genetics and some health conditions can impact your body weight. Your weight is primarily a function of diet and lifestyle. By definition, diet is the kinds of food you habitually eat. We also know diet to mean a specific course of food you restrict yourself for medical reasons or lose weight. Diets restrict calories, limit certain foods or increase particular foods. There are many varying opinions on diet, and there is no definitive research to support one ideal diet for everyone. This episode provides an overview of popular diets and considerations for continuing or starting these diets during pregnancy. Learn about weight gain during pregnancy and the safety of diets like caloric restriction, low glycemic, keto, paleo, low fat, the Louwen diet for pregnancy, and intermittent fasting. Plus, what your diet goal should be and what to eat when you are pregnant.

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Pregnancy involves weight gain, and your care provider uses this metric to measure your health and the health of your baby. Nine months is a long time to be stressed out about your weight. Not to mention the social pressure to lose weight after you have your baby. The physical changes you will go through can lead to some challenges with your body image.

While many factors like genetics and some health conditions influence your weight, your weight is primarily a function of diet and lifestyle. By definition, diet is the kinds of food you habitually eat. We also know diet to mean a specific course of food you restrict yourself for medical reasons or lose weight. Many different diets limit calories, limit certain foods or increase particular foods. There are also many varying opinions on diet. There is no definitive research to support one ideal diet for everyone, and nutrition is very individualized. This article provides an overview of popular diets and considerations for continuing or starting these diets during pregnancy. Read on to learn about weight gain during pregnancy and the safety of diets like caloric restriction, low glycemic, keto, paleo, low fat, the Louwen diet for pregnancy, and intermittent fasting.

The Limitations of Research on Diet and Nutrition

Studies on the long-term effects of consuming any food are complicated because there are so many variables. If you increase your consumption of one food, you are likely to decrease your consumption of something else. We do not know whether the change in health or disease is related to eating more of one food or less of another.

Another challenge with research on nutrition and diet is that most studies rely on questionnaires that require participants to self-report on the foods they consume. The problem is that the reporting is typically not very accurate. On top of the challenges to having an evidence-based approach to what the right diet is, there is not a one-size-fits-all. Everyone is different. We have different dietary needs based on our genetic makeup, location, activity levels, health, etc.

Increased Nutrient Requirements in Pregnancy

During pregnancy, you have many increased requirements for nutrients. You have increased energy demands, and you have to supply your baby with everything they need to grow. The foods you eat should be your primary source for all of the vitamins and nutrients you and your baby need. You should also be taking a prenatal vitamin to fill in any gaps of nutrients that can happen with any diet.

Weight Gain During Pregnancy

Care providers look at weight gain during pregnancy to make sure you are gaining a healthy amount of weight. Excessive weight gain or not gaining enough weight during pregnancy is associated with low and high birth weights for newborns, preterm delivery, gestational diabetes, preeclampsia, cesarean birth, and postpartum hemorrhage. Your risk for these complications is lower if you gain a healthy amount of weight during your pregnancy.

The American College of Obstetricians and Gynecologists adopts their guidelines on how much weight you should gain during pregnancy from the Institute of Medicine. ACOG recommends that practitioners determine a woman’s Body Mass Index (BMI) at the initial prenatal visit to counsel her on appropriate weight gain during pregnancy. BMI is a calculation of your weight in kilograms divided by your height in meters squared. You can use this calculator to determine your BMI.

The four BMI classifications are:

  • Underweight BMI <18.5
  • Normal weight BMI 18.5-24.9
  • Overweight BMI 25-29.9
  • Obese BMI >30

BMI isn’t a perfect gauge of your health, and this calculation has limits. While it estimates body fat, it can over or underestimate body fat if you have a muscular build or if you have lost muscle.

If you are underweight, your care provider expects you to gain more and gain less if you are overweight. These ranges are for singleton pregnancies, and if you are pregnant with twins, the weight ranges are higher.

  • Underweight (BMI <18.5) 28-40 lbs
  • Normal weight (18.5-24.9) 25-35 lbs
  • Overweight (25-29.9) 15-25 lbs (6.8-11.3 kg)
  • Obese BMI (>30) 11-20 lbs

According to ACOG, there have been some controversial reactions from some physicians who believe that the weight gain targets are too high, especially for overweight and obese women. Concerns have also been raised that the guidelines do not differentiate degrees of obesity, especially for morbidly obese women. The overall recommendation is that the guidelines from the Institute of Medicine provide a basis for practice. Individualized care and clinical judgment are necessary for managing the overweight or obese woman who gains (or wishes to gain) less weight than recommended but has an appropriately growing fetus. Balancing the risks of fetal growth (in the large-for-gestational-age fetus and the small-for-gestational-age fetus), obstetric complications, and maternal weight retention is essential but will remain challenging until research provides evidence to further refine the recommendations for gestational weight gain, especially among women with high degrees of obesity.

Stepping on the Scale

It is routine for most care providers to ask you to step on a scale at the beginning of every prenatal appointment. This can give some pregnant mothers anxiety about whether they are gaining too much weight or not enough. Typically, you will weigh more at each appointment. Keep in mind the weight you gain when you are pregnant isn’t all just fat or weight in your belly. The following figures are estimates and averages, and every woman is different. This should give you some guidelines of where the weight you gain comes from.

  • Breasts grow 1 to 3 pounds (0.5 to 1.4 kilograms)
  • A larger uterus adds 2 pounds (0.9 kilograms)
  • The placenta at birth is about 1.5 pounds (0.7 kilograms)
  • 2 pounds (0.9 kilograms) in amniotic fluid
  • Increased blood volume adds 3 to 4 pounds (1.4 to 1.8 kilograms)
  • The increased fluid volume contributes to another 2 to 3 pounds (0.9 to 1.4 kilograms)
  • Fat stores add about 6 to 8 pounds (2.7 to 3.6 kilograms).
  • By the end of your pregnancy, your baby weighs an average of 7 or 8 pounds (3 to 3.6 kilograms).

Weight Gain by Trimester

Weight gain is not linear throughout the whole nine months of your pregnancy. In the first trimester, you should only gain a few pounds. You should experience a steady, gradual weight gain throughout your pregnancy in the second and third trimesters. You can expect around one pound per week if you start underweight or at a normal weight, and half a pound a week if you are overweight or obese.

Weight Gain in the Real World

Even with these guidelines in place in 2009, most women are not gaining weight within the suggested ranges. One study that looked at over 18,000 pregnancies found that just 25.8% of women gained weight within the recommended ranges, with 21.3% gaining less and 52.9% gaining above. This was across the board for all women regardless of their pre-pregnancy weight.

Your Pregnancy Diet Goal

Whatever your long-term goals for weight or health, you have one priority when you are pregnant – to make sure you and your baby are healthy and what you eat plays a big part in that. You know what the guidelines are and that most women are not gaining weight within those guidelines. Whether you are eating healthy now or need to clean up your diet, pregnancy is an excellent opportunity to focus on eating a healthy diet and developing or maintaining healthy eating habits. That could mean counting calories, adding in more fruits or veggies, or cutting out sugar.


Calories are the measure of the amount of energy in a food or drink. You take in calories from your diet and burn calories with all physical activity, from breathing and thinking to working out. When you consume more calories than you burn, your body stores those extra calories as fat, and over time this can cause weight gain. Calories can be a helpful tool, but not all calories are equal. One hundred calories in sugar do not affect you in the same way 100 calories of protein does.

Calorie Needs During Pregnancy

The standard adult needs about 2,000 calories per day. This figure varies depending on many factors, including age, sex, activity level, and whether you are pregnant or breastfeeding. You can use this calculator to find the daily nutrient recommendations for you. This tool is for healthcare professionals and provides a lot of information, including a breakdown of macronutrients (carbohydrates, protein, fat) and vitamins and minerals.

The American College of Obstetricians and Gynecologists states that no extra calories are needed in the first trimester if you are pregnant with a single baby. In the second trimester, you will need an additional 340 calories per day, and in the third trimester, about 450 extra calories a day.

Calorie Restriction Diets

Diets that restrict calories aim at weight loss since you reduce the number of calories you consume below the number you use for energy. If you consider reducing the number of calories you consume during pregnancy, please discuss it with your doctor or midwife first. Pregnancy is a critical time for development, and you need to focus on growing a healthy baby, not losing weight.

Some animal studies, like this animal study, observed that rats on a calorie-restricted diet gained less weight during pregnancy. The offspring of the rats on a calorie-restricted diet during pregnancy gained more weight later in life. Researchers also measured alterations in endocannabinoid levels in offspring, which is involved in metabolic and behavioral programming.

Low Carbohydrate, Low Sugar, and Keto Diets

Low carbohydrate diets like Atkins or South Beach aim to cut down on carbohydrates. Many people experience initial weight loss, suppression of appetite, feel like they have more energy, and have improved health. Your body uses carbohydrates, in the form of glucose, for fuel. When you are very low on carbs, your body can use ketones for energy instead. The Keto diet nearly eliminates carbs to focus on increasing your ketone levels and burning ketones for fuel.

Since low carbohydrate diets are also low in sugar, they are attractive for someone with gestational diabetes. A randomized controlled trial looked at treating gestational diabetes with a low carbohydrate diet and found no difference in insulin requirements or pregnancy outcomes. This study compared a diet of 40% carbs vs. 55%. One paper published suggested that while carbohydrate restriction results in improved maternal glycemia, similar and potentially more favorable outcomes may be achieved by less-restrictive approaches that include an optimal mixture of higher-quality carbohydrates with lower glycemic index and lower fat. A less restrictive nutritional approach may ease the anxiety associated with the diagnosis and plan for therapy.

Another study proposed that an unbalanced maternal diet may create babies with higher levels of cortisol. They took mothers who were instructed to avoid carbohydrate-rich foods and measured cortisol in their children nearly 30 years later. Of course, like most studies on diet, this is assuming that the mothers followed the diet they were supposed to.

There is a difference between cutting down on carbohydrates and nearly eliminating them with a diet like keto. If you are considering any type of low-carb diet, please discuss it with your doctor or midwife. It may also be helpful to talk about your goals and why this type of diet appeals to you.

Even if you are not interested in reducing carbs, there are benefits to reducing sugar. Sugar is a broad term for a lot of different molecules that make foods and drinks sweet. Over the years, we have steadily increased the amount of sugar in our diets. Data shows that back in the 1970s, the average American consumed about 37 grams per day. Now that number is up to 55 grams per day. Children consume even more sugar, with an average of 73 grams per day. Sugar is in just about every food and drinks we consume.

How your body processes different types of sugar varies. Plus, during pregnancy, there are changes to the way your body reacts to and processes glucose. For more information on sugar and its effects on you and your baby, see this article.

Louwen Diet

Dr. Frank Louwen is the head of obstetrics and prenatal medicine at the Frankfurt University hospital in Germany. Dr. Louwen came up with the Louwen diet, a low glycemic diet in the last several weeks of pregnancy for an easier labor. He has published a lot of research on obesity, hypertensive disorders, and breech birth. Unfortunately, much of his work is in German, and I had difficulty finding any information from him as the source on the Louwen diet.

In articles online, you can find posts that the Louwen diet will make your labor easier, create a smaller baby, and result in a less painful birth. This diet restricts high glycemic foods from week 32 until birth. The glycemic index is a value assigned to foods based on how quickly they increase your blood sugar (glucose). If you want to check out a list of common foods and how they rank on the glycemic index, click here.

The idea behind the Louwen diet is that when you consume high glycemic foods, this increases your insulin levels, which can hinder the release of prostaglandins. Prostaglandins are released leading up to labor and help soften the cervix to prepare it for effacing and dilating. Synthetic prostaglandins like misoprostol (brand name Cytotec) and dinoprostone (brand names Cervidil and Prepidil) can induce labor. Prostaglandins can also play a role in reducing pain. This is one of many things at play in the symphony of hormones during birth.

I could not locate any research explicitly looking at limiting foods high on the glycemic index in the last 6+ weeks of pregnancy. If you want to read more about the Louwen diet, see this blog post. I also do not see a downside to doing this since limiting sugar is will overall benefit your health. If you choose to restrict foods high on the glycemic index, this may rule out eating dates in the last few weeks, which some evidence shows may make for an easier labor.

Low-Fat Diets

In 2016 evidence showed that the sugar industry sponsored a research program in the 1960s and 1970s that cast doubt about the hazards of sugar while promoting fat as the dietary culprit in coronary heart disease. The sugar industry did not disclose its role in funding and directing this research. For decades fat was blamed for heart disease, and it was thought that eating fat would cause unhealthy weight gain. In recent years, there have been strong arguments that fat is not as bad as the health community has portrayed it. In fact, some fats are good for you. You need fat from your diet, and it is an essential nutrient. However, there are different types of fat.

Trans fats are produced in small amounts naturally in the stomachs of ruminant animals like cows. These fats can also be artificially made in partially hydrogenated oils. As of January 1, 2020, the FDA banned the use of artificial trans fats from partially hydrogenated oils in food by stripping them of the GRAS (generally recognized as safe) label.

Saturated fats come primarily from animal sources. These are usually solid at room temperature. Plant sources of saturated fats are coconut & palm oil.

Monounsaturated fats are in olive, peanut, and canola oils, avocados, almonds, pumpkin, and sesame seeds. These oils are typically Liquid at room temperature, solid in the fridge, and oxidize in high heat.

Polyunsaturated fats include omega 3 and omega 6 oils. An omega 3, DHA, is is a major structural fat in the human brain and eyes. This fatty acid represents about 97% of all omega-3 fats in the brain and 93% of all omega-3 fats in the retina. DHA is crucial for your baby’s development of their brain and retinas during the third trimester and up to 18 months of life. There is a pile of evidence to back up the need for omega 3s and DHA when pregnant.

American and many western diets contain many oils high in linoleic acid, which is an omega 6.  This is high in corn oil, soybean oil, safflower oil, cottonseed oil, sunflower oil. Diets in many western countries have a very high ratio of Omega 6s to Omega 3s. In the US, the range is somewhere between 10-25 times as much omega 6 as omega 3. The ratio should be more like 4 to 1 or even 1 to 1. The issue with this high ratio is that Omega 6s can impact your body’s ability to convert ALA to DHA and EPA. Plus, omega 6s can cause inflammation.

You already know you should strive to eat whole foods rather than processed foods. That is a great start to cut back on some of these oils and lower your intake of Omega 6s to get closer to that 4 to 1 or 1 to 1 ratio which is ideal.

The bottom line is that fat isn’t necessarily bad. Many foods that advertise that they are fat-free or low in fat have added sugars. You have to go beyond the bold print on the front of the label and look at the ingredients or the nutrition facts label. If you aim to reduce the fat in your diet drastically, you will also miss out on healthy fats you and your baby need.

Plant-Based Diets

There are many reasons people choose to eat a plant-based diet, including environmental, ethical, or health reasons. Regardless of your reasons for eating a plant-based diet, there is no denying that many animal products are rich in vitamins and nutrients. If you avoid meats, seafood, eggs, or dairy, you need to get nutrients from other sources. While it is possible to eat a healthy diet that does not include animal products, you need to be mindful to make sure you are getting the nutrients you and your baby need. See this article for an in-depth review of protein, vitamins, and nutrients to pay attention to on a plant-based diet.


On the opposite end of the spectrum from a plant-based diet is the carnivore diet. The carnivore diet focuses on mainly eating animal foods and, as a result, restricts carbohydrates. This diet can range from primarily eating animal-based foods to eliminating all plants and incorporating many organ meats. The carnivore diet has gained traction because many people are finding benefits like weight loss and increased energy. Many people also experience an improvement in autoimmune disease, which may result from the carnivore diet being an elimination diet that removes everything except animal products.

While it may sound crazy to eliminate plants from your diet, there are proponents like Dr. Paul Saladino who make a good case for eating carnivore.

There is no research on the carnivore diet and pregnancy. It is possible to get all of the vitamins and nutrients you need from only animal products if you include nutrient-rich organ meats. Plus, the quality of meat matters, and a grass-fed steak is different from a hotdog. The carnivore diet is the most restrictive diet discussed in this article. Please do your research and talk to your doctor or midwife to make sure you are meeting all of your nutrient requirements.

Paleo Diet

The paleo diet focuses on foods that would have been available during the paleolithic era, from about 2.5 million to 10,000 years ago. This diet eliminates all processed foods and foods that were not consumed by our ancestors, like dairy, legumes, and grains. This is touted as a good diet for weight loss, which, remember, should not be your primary goal during pregnancy. There are obvious benefits to cutting out sugar and processed foods, which the paleo diet does. I could not locate any research specific to the paleo diet and pregnancy.

Intermittent Fasting

Intermittent fasting is limiting your food intake to a shortened window. For example, you could eat in an eight-hour window between 9:00 am and 5:00 pm, then fast for 16 hours. Typically, there is no restriction on what you eat during your feeding window. When you are fasting, you can and should drink water or other zero-calorie beverages, like tea. There is a lot of evidence that intermittent fasting improves glucose regulation, increases stress resistance, and suppresses inflammation.

A systematic review and meta-analysis looked at the research of pregnant mothers who fasted for Ramadan. This is a month-long period when Muslims fast from sunrise to sunset. Interestingly, expectant mothers are exempt from this practice, although many do participate. This included 22 studies of 31,374 pregnancies, of which 18,920 pregnancies were exposed to Ramadan fasting. The researchers found Ramadan fasting does not adversely affect birth weight, although there is insufficient evidence regarding potential effects on other perinatal outcomes. Further studies are needed to accurately determine whether Ramadan fasting is associated with adverse maternal or neonatal outcomes.

Keep in mind this was only for intermittent fasting for one month or shorter, not for the length of a pregnancy. Lily Nichols has a great post with a lot of evidence on why intermittent fasting is a mismatch for pregnancy. If you are considering intermittent fasting, please read her well-researched thoughts on the topic.

Click Bait Headlines

A study titled “Low carbohydrate diets may increase risk of neural tube defects” sent many low-carb fans into a panic that their diet could cause congenital disabilities. These headlines are aimed at getting clicks, not at delivering what this study actually found. Chris Kresser has a great article breaking down this study and pinpointing that it was more likely a lack of folate than low-carb that caused the neural tube defects. You know you need adequate folate, and you should be getting that from your diet and prenatal vitamin.

Another example of this can be found in a study on the DASH (Dietary Approaches to Stop Hypertension) diet. This diet emphasizes eating more fruits, vegetables, whole grains, nuts, and lean protein. A study of overweight and obese women split the participants into two groups: coaching on the DASH diet and physical activity and the control group who had no coaching. Researchers measured weight gain and concluded those in the intervention group gained significantly less weight. There were no significant differences in adverse pregnancy outcomes, but there were more cesarean births in the group that received the coaching. While this study found statistically significant differences in weight gain, it amounted to five pounds less over the course of pregnancy.

Every day a new click-bait headline pops up with the “19 Best Foods for Pregnancy” or ”Pregnancy week-by-week meal plans.” There will always be hype around diets, and if there were one perfect diet for everyone, we would all be on it.

Diet Tips

The closest thing to a perfect diet will be to eat healthy whole foods. The bulk of your diet should be foods that were alive, whether this is plants or animals. You should be limiting processed foods. If it has a long ingredient list or things that you cannot pronounce or have never heard of, it is probably processed. “Real food,” as Lily Nichols, RDN, CDE puts it in her book, Real Food for Pregnancy. She writes, “In a nutshell, real food is made with simple ingredients that are as close to nature as possible and not processed in a way that removes nutrients.” If you want an evidence-based deep dive into what you should eat during pregnancy, I highly recommend her book.

Tips to modify your diet in the right direction.

  • Limiting sugar is always a good idea. The keyword here is limiting. If you can eliminate this, great. It is okay to enjoy dessert or sweets occasionally.
  • A good measurement of how well you are eating is how you feel. Pregnancy can come with fatigue and nausea that have nothing to do with your diet. Plus, it can be challenging to eat a wide variety of foods if you are experiencing morning sickness. Adjust your diet as needed. Your calorie requirements increase in the second and third trimesters, which requires you to eat more or consume more calorie-dense foods. If you feel like the diet you are eating is not working, change it.
  • Do not focus on weight loss; focus on eating well. If you are continuing or trying a specific diet, ask yourself what your goal is. If it is weight loss, it may not be a great fit during pregnancy.
  • You should talk to your doctor or midwife about any diet that is restrictive with a macronutrient like carbohydrates or fat or that restricts calories.

Food Cravings, Cheat Meals, and Treats

Many expecting mothers experience different food cravings during pregnancy. There is some speculation that if you crave a particular type of food, your body is trying to balance a nutrient deficiency. For example, if you are craving oranges, you need more vitamin C. Research doesn’t support that theory, and food cravings are likely psychological. You can indulge in food cravings that are not the healthiest options, just do not overdo it.

If your diet is too restrictive, it can be challenging to stick to it. Do not beat yourself up if you enjoy a meal outside of your diet or that is not healthy. You can eat relatively healthy and enjoy a sugary treat. It takes time to build healthy eating habits and work towards eating primarily healthy whole foods.

How to make Eating Healthy Easier

You can do so many simple things to make eating healthily more accessible and more of a habit than a chore. Here are some tips to make it easier:

  • Meal plan before grocery shopping so you don’t buy foods that you shouldn’t have.
  • If you have trouble sticking to a list or don’t like reading labels at the store, try shopping online and getting your groceries delivered.
  • It can be time-consuming to cook meals from scratch. If you batch meal prep and cooking by making several meals or servings at once, you can save time. If you want to shortcut meal prep, many meal delivery services with premade meals, like Freshly, make eating healthy so easy.
  • Don’t force yourself to eat foods you don’t like. It does not matter how healthy something is; if you do not enjoy eating it, skip it. There are so many options. With a bit of experimentation, you can find healthy foods that you love to eat.
  • A powerful tool for making sure you are eating well is to keep a food journal. You don’t have to do this for your entire pregnancy. Even keeping track of meals for a week and reviewing what you ate can help pinpoint where you can improve.
  • It takes time to make eating a healthy diet a habit. Plus, there can be a big learning curve to know what foods are good and which you should avoid. If you are new to reading nutrition labels, it can be daunting at first. Over time, this does get easier. The time you spend upfront will pay off in the long run.

Eating Disorders

9.2% of women pre-pregnancy and 7.5% of pregnant women have an eating disorder. These percentages are for disorders that are clinically diagnosed. The diet industry is a $40 billion per year industry. Diet companies gear marketing towards making you feel like you have to go on a diet to fit some standard of what your body should look like.

There is some good news: those who have an eating disorder before getting pregnant generally tend to improve during pregnancy. That doesn’t mean that it is easy or that they do not struggle. Keep in mind that pregnancy can cause past easing disorders to resurface, causing relapse.

If you have any questions about eating disorders or negative habits around eating, please bring them up with your doctor or midwife. If you have dealt with an eating disorder in the past, or are currently dealing with one, talk to your care provider, seek out a midwife or OBGYN who has experience with patients who have had eating disorders. You need to know that you are not alone in this struggle and there are resources to help. A great start is to talk to your doctor or midwife.

Talk to Your Doctor or Midwife

Hopefully, your care provider is knowledgeable and up to date on nutrients, vitamins, and diet. If you have any questions about your diet or whether you are meeting the requirements for nutrients you and your baby need, please talk to your doctor or midwife. You may need to consult a dietician or do your research to advocate for yourself if you are not getting sufficient answers to your questions. If you are concerned that you are deficient in any vitamins or nutrients, you can always request a test. You can run a panel on a blood sample to find out what your levels of all the needed vitamins and nutrients are.

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