The Definitive Benefits of a Low-Fat, Plant-Based, Whole-Food Diet

Article written and reviewed by Cyrus Khambatta, PhD and Robby Barbaro, MPH
Published May 4, 2022

So Why Are We Talking About This Diet?

The low-fat, plant-based, whole-food diet (which we sometimes call the “green light” diet for short) really isn’t anything new. In fact, when you look at the research, it’s probably the closest to what most humans have been eating most of the time for the majority of human history. 

So why are we talking about it now? Well, with the meteoric rise of obesity, diabetes, and chronic diseases in the past century, dietary scientists have been taking some time to reassess exactly what it is we’re eating and how it affects our overall health. 

And whether those scientists have been searching for ways to live longer, lose weight, avoid chronic diseases, or reverse diabetes, the results have pointed pretty closely to one answer — the low-fat, plant-based, whole-food diet. 

Here at Mastering Diabetes, we settled on the low-fat, plant-based, whole-food diet as a result of decades of personal experience living with type 1 diabetes combined with countless hours of research, and review of thousands upon thousands of scientific studies. 

First and foremost, this diet was selected to help other people living with diabetes reverse insulin resistance and take control of their diabetes health. But the benefits of the green light diet extend far beyond just reversing insulin resistance and type 2 diabetes. 

That’s why in this article, we’ll be exploring the many, many health benefits of a low-fat, plant-based, whole-food diet. 

Defining the “Green Light” Diet

The low-fat, plant-based, whole-food diet prescribed by Mastering Diabetes (often called the “green light” diet) divides foods into three categories. 

Green Light Foods | Consumed Ad Libitum

The green light category contains the foods that you can eat ad libitum (i.e. as much as you want). These are all unrefined whole foods that are optimal for reversing insulin resistance and there is no need to limit how much to eat.

Green light foods include:

  • Fruits (e.g., bananas, mangoes, oranges)

  • Starchy vegetables (e.g., potatoes, butternut squash, corn)

  • Legumes (e.g., beans, lentils, peas)

  • Intact whole grains (e.g., brown rice, quinoa, farro)

  • Non-starchy vegetables (e.g., tomatoes, cucumbers, broccoli)

  • Leafy greens (e.g., lettuce, arugula, spinach)

  • Herbs and spices (fresh or dried)

  • Mushrooms (e.g., shiitake, cremini, portobello)

Yellow Light | Healthy, not Ad Libitum

The yellow light category contains foods that you can include in small quantities because they are either slightly processed, have a higher fat content, or contain high levels of salt. They shouldn’t be daily staples, but they are still considered “healthy” choices.

Yellow light foods include: 

  • Avocados

  • Nuts and seeds

  • Nut and seed butters

  • Plant-based milks

  • Coconut meat

  • Soy products (e.g., edamame, tofu, tempeh)

  • Olives

  • Pasta alternatives (e.g., lentil, bean, brown rice)

  • Sprouted bread

  • Dried fruits (e.g., dates, raisins, dried apricots)

  • Fermented foods (e.g., sauerkraut, kimchi, coconut kefir)

Red Light | Limit or Removed from Diet

The red light category contains the foods that we recommend limiting or completely removing from your fridge, your kitchen cabinets, and most importantly your plate. Followers of the “green light” diet seek to avoid red light foods entirely.

Red light foods include:

  • Red meat

  • White meat

  • Eggs

  • All dairy products

  • Oils of any kind

  • Fish and shellfish

  • Processed baked goods (e.g., croissants, muffins, cookies)

  • Sweeteners (e.g., HFCS, sorbitol, maltodextrin)

  • Refined “white” foods (e.g., white pasta, white bread, white sugar, white flour)

  • Coconut products (processed, high-calorie products excluding coconut kefir and aminos, e.g., yogurt, ice cream)

  • Processed vegan foods (e.g., processed veggie burgers, vegan cheeses, nut milk ice creams)

At a Glance

The Definitive Benefits

For the sake of this article, we’ll be reviewing a number of systematic reviews and large-scale studies for plant-based, vegan, and vegetarian diets that share the majority of these dietary guidelines. 

It’s worth noting that many large-scale studies comply with these diets for the vast majority of nutrition, but may have small differences in the exact specifications. However, as a whole, we believe they represent guidelines that are, for all intents and purposes, in line with the green light diet. 

The Founding Purpose | Diabetes Health

First, let’s take a look at the research as it pertains to the founding purpose of the green light diet — reversing insulin resistance, reversing non-insulin-dependent type 2 diabetes, and managing type 1 diabetes, type 1.5 diabetes, and insulin-dependent type 2 diabetes.

And for this purpose, the evidence is clear. Studies have shown that plant-based diets are found to reduce the risk for insulin resistance, prediabetes, and type 2 diabetes, and lead to higher insulin sensitivity (a key marker in both type 1 and type 2 diabetes). 

This was true across almost all key markers of diabetes. One study showed conclusive advantages in A1c thanks to a plant-based diet while improving healthy body weight and overall health. 

Conversely, numerous studies have shown that meats, especially red meats, drastically increased the risk of type 2 diabetes, along with other comorbidities like cardiovascular disease.

The results were similarly negative for processed foods — which have been shown to inhibit blood glucose control — likely due to the fact that these higher-calorie foods result in similar, or lower, usable energy for the body as comparable whole foods.

It also goes without saying that a high-fat diet is contrary to diabetes health, with numerous studies showing that they decrease insulin sensitivity and induce insulin resistance not just in muscle but also in other organs throughout the body.  

So the research shows that this is the right diet for what it was founded for, but how does it provide other benefits?

Weight Control

One key benefit of this diet is improved weight control. Studies have shown that a plant-based diet is better for weight control, drawing from a number of large-scale epidemiological studies

A low-fat diet helps with your weight as well, with studies showing a high-fat diet helps induce obesity, with significantly more individuals becoming obese under a high-fat diet

This difficulty in weight control also extends to processed foods, which are also strongly correlated with obesity

Improve Cardiovascular Health

It would be easy to draw a line out from the plant-based diet’s benefits for weight control and assume that plant-based diets are advantageous for cardiovascular health. However, the studies do this for us. 

Individuals who follow plant-based diets mark consistently higher on all indicators of cardiovascular health, notably including marked differences in cholesterol as well as significantly better blood pressure than meat-eaters.

Meanwhile, studies have shown that meat-eaters were far more likely to develop cardiovascular disease, especially those who ate red meat or processed meat. We go into the relative risks of cardiovascular disease with a low-fat, plant-based, whole-food diet below. 

Improved Brain Health

Much like the line between obesity and cardiovascular disease, it would be easy to draw a line between improved cardiovascular health and improved brain health. After all, the two have been shown to be clearly linked.

But again, the research also shows promising possible benefits here, including key markers of executive control and brain function

There are also a number of key factors showing that a plant-based diet can help combat cognitive decline and neurodegenerative disease, which we will mention further below. 

Improved Digestive and Gut Health

Moving on into the digestive system, a plant-based diet also has clear benefits. Studies have shown that plant-based diets are effective in promoting gut health, providing positive effects like an increased metabolic performance of intestinal microbiota and improved presence of positive flora.

The opposite is true for diets high in fat as well as for diets high in processed foods. Studies showed that high-fat diets led to an increased risk of gastrointestinal disease, while processed foods led to negative changes in gut composition and increased inflammation.

Improved Skin and Hair Health

The health benefits of the green light diet aren’t limited to internal benefits either. Studies have shown that the phytochemicals from eating a high-plant diet benefit skin health, which is compounded by the fact that these high-antioxidant foods help prevent oxidative stress (which damages skin).

These nutrients similarly benefit your hair, as opposed to high-fat diets, which have been shown to increase oxidative stress, and diets high in processed foods, whose lack of key nutrients has been tied to hair damage

This is another area where there are also significant long-term effects, which we’ll address below.

Reduced Risk of Disease

And in addition to improving your health, a green light diet has a number of benefits that help prevent the incidence of disease. 

Increased Immunity

First, when it comes to general immunity, the high level of antioxidants in a plant-based diet is very beneficial, thanks to their role in supporting the immune system. Research also shows that the vast majority of key nutrients needed by your immune system are found in plants

Conversely, diets high in processed foods are being shown to increase the incidence of compromised immunity, a concerning correlation that may also be true for high-fat diets. 

A word on the high-fat diet correlation with reduced immunity — while these tests have currently been limited to animal trials, so they don’t have a clinical basis yet, early signs suggest that high-fat diets may be harmful to immunity. We’ll keep this article updated as further clinical trials produce results.

Decreased Risk of Cardiovascular Disease

Next up is cardiovascular disease, one of the leading causes of death in the US. We mentioned above that there’s a distinct cardiovascular benefit of eating plants, but you also avoid a negative effect.

For example, red meat, even unprocessed, drastically increases your risk of cardiovascular disease. This isn’t just confined to red meat — eggs and other fats from animals were all associated with cardiovascular disease. 

Saturated and processed fats are the biggest culprit here, and the effects of processed foods didn’t stop there. 

Studies have shown that these processed foods were correlated with increased cardiovascular disease, with one clearly showing a positive correlation between processed food, cholesterol, and blood pressure

Reduced Risk of Stroke

There aren’t as many long-term studies specifically showing the benefits of plant-based diets on stroke, but they have been shown to affect risk factors, and the studies that have been done have provided strong evidence.

And again, the alternatives do show some strong risk of stroke. Red meat has been tied to stroke, especially ischemic stroke, though the exact mechanism is still unclear. 

It may be tied to fat — after all, in animal trials, high-fat diets led to an increased risk of stroke, and this effect was shown in multiple trials — but until we have clinical studies, it’s not possible to say. 

One thing that we can say is that cardiovascular health was certainly negatively affected by processed food, which caused elevated heart age and increased the risk of stroke (similar to red meat and eggs).

Decreased Cancer Risk

And speaking of diseases that affect a large portion of the population, it seems that a green light diet decreases your cancer risk. 

First, we’ll address the elephant in the room — meat consumption is directly correlated with cancer risk. This is true of red meat and processed meat especially, which have a strong enough correlation to digestive tract and other cancers that certain meats have been classified as known carcinogens.

On the other hand, a plant-based diet has been correlated with a decreased risk of cancers, including prostate cancer, along with cancer and heart disease in general. This isn’t a one-off either, and the evidence seems to be clear, consistent, and growing that plant-based diets reduce cancer risk.

Kidney Disease

The benefits of a plant-based diet continue to other organs as well. Studies have shown that plants help prevent kidney disease, and decrease the risks of complications in your kidneys

This has happened in both small and large-scale studies, which show that kidney disease was less prominent in plant-based eaters, while consumption of red meat, a diet high in fat, and processed foods (especially processed fat) were all correlated with increased kidney disease risk.

Liver Disease

You can see a similar effect in your liver, where a plant-based diet has been shown to promote liver health, and may actually have a healing effect on your liver. 

Either way, plant-based individuals had lower odds of liver disease than red meat eaters, who had a high rate of liver disease

Once again, the same was true of a high-fat diet, which was clearly correlated with a higher incidence of liver disease. And unsurprisingly, you can see the same results with processed foods, which increase the risk of nonalcoholic fatty liver disease.


And the final, major group of benefits of a green-light diet pertains to longevity and long-term health.

All-Cause Mortality Risk

First and foremost, eating a plant-based diet is correlated with reduced all-cause mortality risk. And this isn’t a one-off correlation. It has been shown again and again, in a number of different cultures and across major long-term studies.

And you can see the reverse from meat consumption, which has a proven increased mortality risk that is similarly in line with high-fat diets, which have also been shown over large studies to increase mortality risk. Processed foods are a risk here too, with a clear correlation between ultra-processed foods and long-term mortality risk.

Reduced Risk of Neurodegenerative Diseases and Cognitive Decline

And it’s not just a case of living longer either. The research is clear that a plant-based diet is the key to aging gracefully and can help prevent the onset of neurodegenerative diseases. 

First, to tie this diet all the way back to diabetes is Alzheimer’s, which many researchers are now referring to as Type 3 diabetes, due to the fact that the main culprit in Alzheimer’s is insulin resistance. This is one possible explanation behind why plant-based dietary patterns have a lower risk of neurodegenerative diseases.

And it’s not just Alzheimer’s. Plant-based diets were associated with increased cognitive function, reduced rate of cognitive decline, and reduced incidence of dementia.

Meanwhile, meat consumption has been shown to be a potential dementia risk, as is a high-fat diet, which may in fact exacerbate Alzheimer’s where it exists.

Reduced Signs of Physical Aging

And though we’re not in the cosmetic industry here at Mastering Diabetes, plant-based diets have been shown to reduce physical signs of aging. The correlation between diet and dermatology is clear here in favor of a plant-based diet, which shows that the key compounds in plants are great for healthy aging

Not to mention that these diets are dense in antioxidants, which are considered to have anti-aging properties and play a massive role in human longevity.

So What’s the Takeaway Here?

Well, a low-fat, plant-based, whole-food diet seems to not only be the secret to reversing diabetes, but it has the keys to living a much longer, healthier, and disease-free life.

And one of the key factors about this diet that we haven’t discussed just yet is the fact that, once adjustments are made to adopt the green light diet (which can be pretty delicious!), it is easy to follow. Plant-based diets are naturally low-fat, and the easiest form of plants to find are also the most minimally processed. 

Add in the lifestyle benefits like improved mood and energy, healthier weight, and lower risk of disease, and you have a diet that is not only better for your health in the long term but naturally incentivizes continuing to follow it. 

If you’re ready to work with a coach, join a supportive community and have accountability to achieve your goals, then book a free discovery call to find out which program is best for you. 

Simply click this link and you’ll be directed to a page where you book a time that works for you and speak with a member of the Mastering Diabetes enrollment team!

About the author 

Cyrus Khambatta, PhD and Robby Barbaro, MPH

Cyrus Khambatta, PhD, and Robby Barbaro, MPH are the coauthors of the New York Times bestselling book Mastering Diabetes: The Revolutionary Method to Reverse Insulin Resistance Permanently in Type 1, Type 1.5, Type 2, Prediabetes, and Gestational Diabetes. They are the cofounders of Mastering Diabetes, a coaching platform that teaches people how to reverse insulin resistance via low-fat, plant-based, whole-food nutrition. Cyrus has been living with type 1 diabetes since 2002, and has an undergraduate degree from Stanford University and a PhD in Nutritional Biochemistry from UC Berkeley. Robby was diagnosed with type 1 diabetes in 2000, and has been living a plant-based lifestyle since 2006. He worked at Forks Over Knives for 6 years, and earned a Master’s in Public Health in 2019.