The Broad Study – A Detailed Look Into a Nutritional Research Study

On March 20, 2017 the results of an interesting study called the BROAD study were published in the journal “Nutrition and Diabetes”. The study was carried out in the rural town of Gisborne, New Zealand and targeted people who were overweight or obese. Many of them also suffered from diabetes or cardiovascular disease. During the course of the BROAD study, participants lost weight, lowered their cholesterol and reversed diabetes while eating unlimited amounts of whole plant foods. Highlight this – participants were advised to eat until full and satisfied and to avoid counting calories. Additionally, in order to understand the power of dietary change alone, participants were not asked to do any exercise.

The “gold” standard….

The BROAD study is an example of the gold standard in research, a randomized controlled trial. The randomization of subjects (deciding which group each participant was to be put into) was done by computer through The study was controlled because the 65 subjects were divided into two groups; one group, the control group, that made no changes in their diets and received standard medical care and the other group, the intervention group, that received education and support to convert to a whole-food plant-based diet. It was not possible to blind this study because each participant made their own food choices within the guidelines of the study. However, the statistician that collected and analyzed the results was blinded. “Blind” or “blinded” in this case means not knowing whether a particular participant is in the control group eating a regular diet or in the intervention group eating a whole-food plant-based diet.

Each participant in the intervention group was given a ‘traffic-light’ diet chart outlining what to eat and what not to eat (see below). Starches such as potatoes, sweet potato, bread, cereals and pasta were encouraged to satisfy the appetite. Intervention group participants followed a low-fat plant-based diet (7 to 15% of total energy from fat) because it is a version of the plant-based diet shown with previous research to achieve the best outcomes for weight loss and heart disease. The intervention group was supported with twice-weekly sessions for the first 12 weeks, teaching them how to transition to a low-fat plant-based whole-food diet in a sustainable manner. A supplement of 50 mcg B12 daily was provided. The control group was given no dietary information. The intervention group was followed for twelve months; the control group was followed for six months.


ULTRA-GREEN (the most nutrient dense and low energy foods available): spinach, kale, Swiss chard, broccoli, turnip and other greens, herbs and spices
GREEN (food to eat every day): vegetables (including starches such as potatoes and sweet potato), fruit, legumes, whole grains (including whole grain bread and pasta), sauces and seasonings without added oil
ORANGE (eat sparingly, if at all): salt; sugar and other sweeteners; processed flour and other processed foods; tempeh and tofu (due to fat content); soy milk, almond milk, oat milk without added oils (due to fat content); caffeine; alcohol
RED (do not eat): poultry, meat, fish, eggs, dairy products, added oils. Strongly limit (due to fat content) nuts, seeds, tahini, avocado, coconut, coconut milk

INTERVENTION GROUP                                         CONTROL GROUP

Decreased medication use by about 30%                                 Increased medication use by about 8%
Weight loss of 18 pounds after 3 months                                 Weight loss of 3 pounds after 3 months
Weight loss of 26 pounds after 6 months                                 Weight loss of 6 pounds after 6 months
Weight loss sustained over 12 months                                      No follow up after 12 months
Cholesterol dropped by 16% after 3 months                            Cholesterol dropped by 3% after 3 months
LDL cholesterol dropped 26% after 3 months                         LDL cholesterol dropped 11% after 3 months
HDL cholesterol dropped by 15% after 3 months                   HDL cholesterol rose 7% after 3 months
Triglycerides increased by 12% after 3 months                       Triglycerides dropped by 7% after 3 months
Total:HDL ratio dropped from 4.3 to 3.9 after 12 mths        Total:HDL ratio started at 4.2 and stayed at 4.2
Drop in average A1C values from 6% to 5.5%                          Rise in average A1C values from 5.5% to 5.7%
Enjoyed increased quality to life and                                         Little change in quality of life and self-esteem
and higher self-esteem


Seven people in the intervention group were living with type 2 diabetes. During the course of the study they all experienced a drop in A1C values (a measurement of average blood glucose over the previous 3 months) and half of them discontinued all their medications. By the end of the study, two of them no longer met the diagnostic criteria for diabetes. In other words, they were not considered to be diabetic any longer.
Participants in the intervention group noticed increased quality of life and higher self-esteem. They also noted no significant change in their enjoyment of food or the cost of their food.


The most likely reason for the weight loss seen in this study is the lower density of the food consumed (lower fat, higher water and fiber). Many participants stated that they were not hungry during the study and that this was an important factor in their ability to adhere to the diet. This adherence did however decrease with time. Reports from participants suggest that family and acquaintances also benefitted from exposure to the whole-food plant-based diet (1).


Total cholesterol was reduced in both groups at 3 months. This reduction continued over the full 12 months for the intervention group. The control group was followed for only 6 months but also held its cholesterol reduction. LDL cholesterol (“bad cholesterol”) also decreased in both groups, although to a much lesser degree in the control group. The reduction in LDL cholesterol in the intervention group during this study is comparable to the effects of statin drugs, but without the side effects (11). HDL cholesterol (“good cholesterol”) levels decreased in the intervention group and increased slightly in the control group. In spite of the ups and downs of various cholesterol components, the total:HDL ratio was lower in the intervention group, pointing to an overall healthier lipid profile (10).

A decrease in HDL has been found to be fairly common among people eating a whole-food plant-based diet (2). The reasons are still unclear however it is argued that increased HDL is a normal response to a high-fat diet. Given that the function of HDL is to facilitate the transport of cholesterol to the liver for removal from the body, it may be that people with lower cholesterol levels do not require as much HDL (6). The value of using HDL levels as a predictor of cardiovascular risk, especially in populations who do not consume a typical western diet, is now being questioned (2). Suffice it to say that studies show that low-HDL along with low-LDL are associated with low risk of coronary disease and that individuals consuming a plant-based diet are at lower risk of cardiovascular disease and type 2 diabetes, despite having lower HDL levels (3,4,5).

In comparison to other weight loss studies, this one achieves at least equal weight loss to that of very low calorie diets which are difficult to stick with, not intended for ongoing use and have a high probability of regaining 50% or more of the lost weight after 1 or 2 years (12). Similar weight loss is shown with low-carbohydrate diets, however, low-carbohydrate diets have been shown scientifically to have higher rates of all-cause mortality (7), decreased blood flow due to decreased arterial dilation ability (endothelium dysfunction) (8) and worsening of coronary artery disease (9). Bariatric surgery results (bariatric surgery drastically reduces the size of the stomach) also compare to these results but carry with them the risk of surgical side effects and death as well as post-surgery weight gain that can result in a body weight of as much or more than that at pre-surgery (13).


Weaknesses in this research are stated by the authors. The intervention group was not perfectly adherent. As adherence decreased, cholesterol increased. Consumption of “green” foods was not monitored and the information was obtained by self-reporting and recall, methods prone to errors. Strengths included the “real world” nature of the study. Skills were provided to community-dwelling adults who were responsible for their own food choices.
A limitation was noted in the necessity to explain the whole-food plant-based diet to all participants during informed consent. Increased testing also may have led to more focus on diet for all participants. Some measure of the observed lipid reductions in the control group may have been affected by this extra knowledge (1).


The BROAD study illustrates how eating a plant-based, whole-food diet that is naturally low in fat will result in weight loss even when food intake is not limited. Beyond weight loss, other health biomarkers such as cholesterol and hemoglobin A1C are improved.



1 Wright, N., Wright, L., Smith, M., Duncan, B., McHugh, P. The BROAD study: A randomised controlled trial using a whole food plant-based diet in the community for obesity, ischaemic heart disease or diabetes. Nutrition & Diabetes 2017; 7, e256

2 Kent, L., Morton, D., Rankin, P. et al. The effect of a low-fat, plant-based lifestyle intervention (CHIP) on serum HDL levels and the implications for metabolic syndrome status – a cohort study. Nutr Metab (Lond). 2013; 10: 58.

3 Ferdowsian, H.R., Barnard, N.D. Effects of plant-based diets on plasma lipids. Am J Cardiol. 2009; 104:947–956.

4 Roberts, C.K., Ng, C., Hama, S., Eliseo, A.J., Barnard, R.J. Effect of a short-term diet and exercise intervention on inflammatory/anti-inflammatory properties of HDL in overweight/obese men with cardiovascular risk factors. J Appl Physiol. 2006; 101 :1727–1732.

5 Barnard, R.J., Guzy, P., Rosenberg, J., O’Brien, L. Effects of an intensive exercise and nutrition program on patients with coronary artery disease: five-year follow-up. J Cardiac Rehab. 1983; 3:183–190.

6 Miller, N.E. HDL metabolism and its role in lipid transport. Eur Heart J. 1990 Dec; 11 Suppl H: 1-3.

7 Noto, H., Goto, A., Tsujimoto, T., Noda, M. Low-carbohydrate diets and all-cause mortality: a systematic review and meta-analysis of observational studies. PLoS ONE 2013; 8: e55030.

8 Schwingshackl, L., Hoffmann, G. Low-carbohydrate diets impair flow-mediated dilatation: evidence from a systematic review and meta-analysis. Br J Nutr 2013; 110: 969–970.

9 Fleming, R.M. The effect of high-protein diets on coronary blood flow. Angiology 2000; 51: 817–826



12 Tsai, A.G., Wadden, T.A. Systematic review: an evaluation of major commercial weight loss programs in the United States. Ann Intern Med 2005; 142: 56–66.

13 Christou, N.V., MacLean, L.D. Weight Gain After Short- and Long-Limb Gastric Bypass in Patients Followed for Longer Than 10 Years. Ann Surg. 2006 Nov; 244(5): 734–740.

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My name is Debra Harley (BScPhm) and I welcome you to my retirement project, this website. Over the course of a life many lessons are learned, altering deeply-rooted ideas and creating new passions.

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