OMA Logo

May 9, 2023

Unlocking the Potential: How the Vegan Diet Can Help with Sustainable Weight Loss

Share this post

image of a person holding a bowl of food up to the camera over a marble table. the bowl has various vegetables and grains

Veganuary may be over, but the vegan movement continues to grow. Many patients come into the office asking about switching to a vegan diet for health benefits and weight loss, and we clinicians must guide them appropriately. First of all, we need to be able to help them understand the difference between a vegan diet vs. a plant-based diet, as often these terms are used interchangeably.

As our previous article on vegan diets mentioned, “The vegan diet is a type of vegetarian diet, but in addition to meats and fish, eggs, and dairy, all other animal products are also avoided. This includes honey, gelatin, certain food colorings, some types of alcohol, and all other animal products.” A vegan diet is a plant-based diet, but not all plant-based diets are vegan. Plant-based diets also encompass other vegetarian diets (i.e., pescatarian or fish/seafood containing vegetarian diets, and ovo-lacto or egg/dairy containing vegetarian diets) as well as semi-vegetarian or flexitarian diets, which do include all animal-based products, but consumed at a lesser frequency than people eating non-vegetarian diets [1]. In a head-to-head trial among plant-based diets for weight loss, vegan diets have been correlated with higher amounts of weight loss than other plant-based diets [2].

The vegan diet/lifestyle has also been popularized in the media as being healthier and better for the planet [3]. What was once considered an alternative diet/lifestyle has now become mainstream. As mentioned, patients are increasingly curious about “going vegan.” Even my patients who have not considered veganism before are more responsive to my recommendations on consuming fewer animal products, especially given the plethora of available plant-based “meats” and dairy alternatives.

While now is a good time to ride the wave of getting patients to eat more vegetables and other non-animal products, it is also essential to remember that not all vegan products are healthy, i.e., plant-based ultra-processed foods. The key to weight loss is still to eat mostly high-fiber, whole or minimally processed, less calorie-dense plant foods in moderation instead of only reducing calories. I continue to counsel patients on using the MyPlate method to determine their portion sizes – ½ plate of fruits and vegetables (as many different colors as possible), ¼ plate of plant-based protein (see options below), ¼ plate of complex carbohydrates (such as whole grains) plus or minus 1 cup of fortified soy milk/yogurt [4]. Eating a variety of whole, minimally processed plant foods helps patients stay full longer (from the fiber, protein, and unsaturated fat content) and obtain the essential nutrients.

Besides portion sizes and variety of foods, there are also potential nutrient deficiencies to counsel patients on:

1. Protein – Good alternative sources for non-animal-based protein are legumes (including soy products, beans, lentils, and peas) and whole grains, nuts, and seeds [4].

Proteins are an essential component of building lean body mass as well as other cellular processes in the body [4]. They are also crucial in weight loss, as adequate intake helps increase fullness, decrease hunger, and preserve muscle mass during weight loss [5]. Protein deficiency can manifest as muscle loss/weakness, osteoporosis, and skin changes [6]. More importantly, many plant protein sources do not contain all nine essential amino acids, so many plant protein sources have to be combined to be a complete source of protein (i.e., brown rice and beans).

Additionally, vegans are particularly at risk of not eating enough of three essential amino acids: lysine, methionine, and tryptophan. Make sure to encourage vegan patients to intake a variety of different plant foods as below:

  • Lysine sources – avocados, wheat germ, and legumes.
  • Methionine sources – wheat, wheat germ, millet, barley, brown rice, corn, kamut, oats, rye, sorghum, teff, triticale, and quinoa.
  • Tryptophan sources – seeds, nuts, legumes, and grains.

Plant foods also do not contain the following three conditionally essential molecules made from amino acids: creatine, carnitine, and taurine [6]. While these molecules can be produced in the body, production can be impaired by increased physiologic stress (including pregnancy, significant and sustained physical exertion, and chronic medical conditions). Consider supplementation in these cases.

2. Vitamin B12 – There are B12-fortified vegan foods (look for the label identifying them as fortified), including nutritional yeast, plant milk, soy products, and cereals [6]. Dried seaweed (also known as nori) is another source of vitamin B12. Deficiencies in B12 can lead to anemia and neurocognitive dysfunction, including symptoms such as memory loss, fatigue, and mood changes.

3. Iron – Good plant sources of iron include leafy greens, quinoa, soy products, sesame, pumpkin seeds, lima beans, lentils, cashews, and almonds [6]. It is best absorbed with vitamin C in citrus fruits, bell peppers, tomatoes, and broccoli. Iron deficiency can lead to anemia, restless leg syndrome, fatigue, and impaired temperature regulation.

4. Essential fatty acids – Alpha-linoleic acid or ALA (short chain omega 3) and linoleic acid (omega 6) cannot be produced by the body and must be ingested [6].

  • ALA sources – walnuts, flaxseeds, hemp seeds, and chia seeds
  • Linoleic acid sources – cold-pressed safflower, sunflower, and olive oils; avocados, nuts, and seeds

Deficiencies in these essential fatty acids can lead to increased inflammation, impairment in fetal development, and changes in mood, memory, cognition [6], and skin [7].

5. Calcium – Good plant sources include almonds, beans, blackstrap molasses, broccoli, dark leafy greens, dried figs, okra, tahini, and soy products [6]. Calcium deficiency can manifest as muscle cramping, muscle spasms, decreased bone density, irregular heart rhythms, and paresthesias.

6. Vitamin D – Non-animal-based sources include sun-exposed mushrooms [6] and fortified foods. Deficiencies manifest as musculoskeletal pain/weakness, fractures, falls, impaired immunity, inflammation, and pregnancy complications.

7. Zinc – Good non-animal-based sources include grains, legumes, wheat germ, soy, nuts, seeds, leafy vegetables, root vegetables, and nutritional yeast [6]. Deficiencies can lead to impaired immunity, wound healing problems, skin/hair/nail changes, infertility, and fetal complications.

Faced with all this, patients may become a bit overwhelmed. Encourage them by reminding them that while vegan diets may require more planning and thinking about their food, the benefits are many – including, but not limited to, weight loss (as mentioned previously), improvements in cardiovascular health, and potentially, lower risks of certain types of cancer [1]. So many existing nutritious and delicious recipes are out there to keep them engaged and motivated to continue this diet. As long as they maintain regular follow-ups with us, their clinicians, we can help troubleshoot any potential issues.

Veganuary may be over, but with our help, healthy vegan weight loss journeys can still flourish.

Le LT, Sabaté J. Beyond meatless, the health effects of vegan diets: findings from the Adventist cohorts. Nutrients. 2014 May 27;6(6):2131-47. doi: 10.3390/nu6062131. Turner-McGrievy GM, Davidson CR, Wingard EE, et al. Comparative effectiveness of plant-based diets for weight loss: a randomized controlled trial of five different diets. Nutrition. 2015 Feb;31(2):350-8. doi: 10.1016/j.nut.2014.09.002. Andrew, A. From fringe to mainstream: how millions got a taste for going vegan. The Guardian [Internet] (US Ed.). 2021 Oct 10 [cited 2023 Apr 24];Lifestyle:[about 7 screens]. Available from: U.S. Department of Agriculture. MyPlate [Internet]. Alexandria, VA:U.S. Department of Agriculture; [cited 2023 Apr 24]. Available from: McCarthy D, Berg A. Weight Loss Strategies and the Risk of Skeletal Muscle Mass Loss. Nutrients. 2021 Jul 20;13(7):2473. doi: 10.3390/nu13072473. Plotnikoff GA, Dobberstein L, Raatz S. Nutritional Assessment of the Symptomatic Patient on a Plant-Based Diet: Seven Key Questions. Nutrients. 2023 Mar 13;15(6):1387. doi: 10.3390/nu15061387. Whelan J, Fritsche K. Linoleic acid. Adv Nutr. 2013 May 1;4(3):311-2. doi: 10.3945/an.113.003772.

Article written by:

Headshot of Jennifer Ng, MD, DABOM, sitting in a white coat with a lab in the background

Jennifer Ng, MD, DABOM

Dr. Jennifer Ng, Dipl ABOM, is an internist with a secondary specialization in obesity medicine. Assistant Professor of Medicine at the Mount Sinai Icahn School of Medicine, she teaches medical students and residents regularly. She currently serves as the committee chair of the Obesity Medicine Association’s (OMA) outreach committee, which aims to raise awareness of obesity medicine among patients and the medical community. Previously, she was also a member of the OMA treatment algorithm committee, which published yearly updates to the treatment guidelines for obesity medicine. She is a regular contributor to the OMA’s blog on obesity medicine and is also an associate editor of the OMA journal Obesity Pillars.