Summary: When designing a dietary strategy for weight loss and maintenance the individual patient’s functional and genetic constitution must be carefully considered, but there is an accumulation of evidence indicating that a high protein, low carbohydrate regimen is a good starting point.

There is a large body of evidence that can instruct us in how to fashion an eating plan to promote both short and long-term success in weight loss and healthy body composition. As a paper published in the journal Obesity demonstrates, the way many Americans eat—referred to as a ‘cafeteria diet’ (CF)—is worse than a diet high in lard. The authors note:

“Obesity has reached epidemic proportions worldwide and reports estimate that American children consume up to 25% of calories from snacks. Several animal models of obesity exist, but studies are lacking that compare high-fat diets (HFD) traditionally used in rodent models of diet-induced obesity (DIO) to diets consisting of food regularly consumed by humans, including high-salt, high-fat, low-fiber, energy dense foods such as cookies, chips, and processed meats.”

They investigated the effects on weight gain and inflammation of a cafeteria diet (CAF) compared to a lard-based 45% HFD by feeding their rodent models either HFD, CAF or a chow control for 15 weeks. Their data clearly show that even consuming almost half the diet in lard is better than the lethal mix that many now consume:

“Body weight increased dramatically and remained significantly elevated in CAF-fed rats compared to all other diets. Glucose- and insulin-tolerance tests revealed that hyperinsulinemia, hyperglycemia, and glucose intolerance were exaggerated in the CAF-fed rats compared to controls and HFD-fed rats.”

Moreover, the cafeteria diet was markedly worse in promoting inflammation:

“It is well-established that macrophages infiltrate metabolic tissues at the onset of weight gain and directly contribute to inflammation, insulin resistance, and obesity. Although both high fat diets resulted in increased adiposity and hepatosteatosis, CAF-fed rats displayed remarkable inflammation in white fat, brown fat and liver compared to HFD and controls. In sum, the CAF provided a robust model of human metabolic syndrome compared to traditional lard-based HFD, creating a phenotype of exaggerated obesity with glucose intolerance and inflammation.”

A study published in The New England Journal of Medicine examined specific dietary factors that stand out in their contribution to obesity noting that they…

“…may affect the success of the straightforward-sounding strategy “eat less and exercise more” for preventing long-term weight gain.”

They performed investigations involving 120,877 U.S. women and men who were free of chronic diseases and not obese at baseline for as long as twenty years. Relationships between changes in lifestyle factors and weight change were evaluated every four years. There were several factors that stood out:

“Within each 4-year period, participants gained an average of 3.35 lb. On the basis of increased daily servings of individual dietary components, 4-year weight change was most strongly associated with the intake of potato chips (1.69 lb), potatoes (1.28 lb), sugar-sweetened beverages (1.00 lb), unprocessed red meats (0.95 lb), and processed meats (0.93 lb) and was inversely associated with the intake of vegetables (−0.22 lb), whole grains (−0.37 lb), fruits (−0.49 lb), nuts (−0.57 lb), and yogurt (−0.82 lb)…Other lifestyle factors were also independently associated with weight change, including physical activity (−1.76 lb across quintiles); alcohol use (0.41 lb per drink per day), smoking (new quitters, 5.17 lb; former smokers, 0.14 lb), sleep (more weight gain with <6 or >8 hours of sleep), and television watching (0.31 lb per hour per day).”

Potatoes are clearly ‘sugar grenades’, but in my opinion further studies are required to examine the difference between red meat from animals treated with hormones and fed a grain diet versus those that are free of growth-stimulating medications and eat mainly grass.

With the most egregious insults to a metabolically healthy diet out of the way, we can proceed to the roles of glycemic index and glycemic load on weight loss as examined in a study published recently in the Journal of Nutrition:

“This study assessed the effect of changes in glycemic index (GI) and load (GL) on weight loss and glycated hemoglobin (HbA1c) among individuals with type 2 diabetes beginning a vegan diet or diet following the 2003 American Diabetes Association (ADA) recommendations.”

99 subjects with type 2 diabetes were randomized to follow 1 of 2 diet treatments for 22 weeks. Glycemic index and glycemic load changes were assessed and their relationships with changes in weight and HbA1C were calculated. (Glycemic index is a metric for rate which a food will cause blood sugar to rise. Glycemic load is determined by multiplying the glycemic index by the amount of carbohydrate in grams provided by a food and dividing the total by 100; this amounts to the sum of the glycemic loads for all foods consumed in the diet.) Interestingly, glycemic index predicted weight gain while glycemic load did not:

“…the vegan group reduced GI to a greater extent than the ADA group, but GL was reduced further in the ADA than the vegan group. GI predicted changes in weight, adjusting for changes in fiber, carbohydrate, fat, alcohol, energy intake, steps per day, group, and demographics, such that for every point decrease in GI, participants lost ~0.2 kg (0.44 lb)…Weight loss was a predictor of changes in HbA1C. GL was not related to weight loss or changes in HbA1C.”

Thus glycemic index takes precedence over glycemic load in choosing foods for weight loss and blood sugar regulation. Also notable was the finding regarding GI and HbA1C:

“GI was not a predictor for changes in HbA1C after controlling for weight loss.”

Every wonder why a patient’s HbA1C didn’t go down even though they were eating a low GI diet? This shows that if they don’t lose weight as a result, the the HbA1C will tend to stay the same. The authors conclude:

“A low-GI diet appears to be one of the determinants of success of a vegan or ADA diet in reducing body weight among people with type 2 diabetes. The reduction of body weight, in turn, was predictive of decreasing HbA1C.”

The interesting difference between the effects of glycemic index and glycemic load revealed here help to explain the inconsistency noted in a review published earlier in journal IUBMB (International Union of Biochemistry and Molecular Biology) Life:

“Recently, due to its possible link to appetite control and metabolism, several clinical studies have assessed the effect of low glycemic index (GI) and glycemic load (GL) diets on weight loss. To determine the application of GI/GL in the prevention and treatment of obesity, we searched several databases and identified 23 clinical trials that examined low GI/GL diets and weight loss as the primary outcome measure.”

Here the pooling of GI and GL seems to have obfuscated the issue. The authors conclude:

“Over the past decade, the body of research that links low GI/GL diets to weight loss has grown rapidly and significantly. While there is a significant amount of inconsistency in the current findings, the majority of studies found a trend that favored low GI/GL diets in weight loss.”

Moreover…

“…the benefits of low GI and GL diets extend beyond weight loss and have favorable effects on obesity-related risk factors such as heart disease and diabetes by mechanisms that are independent of weight loss.”

What about protein versus carbohydrate for weight loss? A number of investigators have examined this question, but an interesting study published recently in the Nutrition Journal corrects some important limitations in earlier work:

“Studies have suggested that moderately high protein diets may be more appropriate than conventional low-fat high carbohydrate diets for individuals at risk of developing the metabolic syndrome and type 2 diabetes. However in most such studies sources of dietary carbohydrate may not have been appropriate and protein intakes may have been excessively high. Thus, in a proof-of-concept study we compared two relatively low-fat weight loss diets – one high in protein and the other high in fiber-rich, minimally processed cereals and legumes – to determine whether a relatively high protein diet has the potential to confer greater benefits.”

They eighty-three overweight or obese women to either a moderately high protein (30% protein, 40% carbohydrate) diet (HP) or to a high fiber, relatively high carbohydrate (50% carbohydrate, > 35 g total dietary fiber, 20% protein) diet (HFib) for 8 weeks. During that time their energy intakes were reduced by 478 to 955 calories per day to achieve weight loss of between 0.5 and 1 kg per week. Which diet resulted in better weight loss?

“Participants on both diets lost weight (HP: -4.5 kg and HFib: -3.3 kg), and reduced total body fat (HP: -4.0 kg and HFib: -2.5 kg, and waist circumference (HP: -5.4 cm and HFib: -4.7 cm), as well as total and LDL cholesterol, triglycerides, fasting plasma glucose and blood pressure. However participants on HP lost more body weight (-1.3 kg) and total body fat (-1.3 kg). Diastolic blood pressure decreased more on HP (-3.7 mm Hg).”

High protein wins out over high carbohydrate, even when the carbohydrate is high fiber. The authors conclude:

“A realistic high protein weight-reducing diet was associated with greater fat loss and lower blood pressure when compared with a high carbohydrate, high fiber diet in high risk overweight and obese women.”

Importantly, the benefits of a high protein to carbohydrate ratio diet include the slowing of tumor growth and prevention of cancer initiation as described in an excellent paper (you may wish to read it in its entirety) published recently in the journal Cancer Research. It includes a significant consideration for reducing carbohydrate by increasing protein rather than fat. The authors state:

“Since cancer cells depend on glucose more than normal cells, we compared the effects of low carbohydrate (CHO) diets to a Western diet on the growth rate of tumors in mice. To avoid caloric restriction–induced effects, we designed the low CHO diets isocaloric with the Western diet by increasing protein rather than fat levels because of the reported tumor-promoting effects of high fat and the immune-stimulating effects of high protein.”

They were able to formulate diets that demonstrated that the tumor inhibiting effects were due to factors other than weight loss from calorie restriction (CR):

“To exploit the fact that cancer cells rely more heavily on glycolysis than normal cells, we designed low CHO, high protein diets to see if we could limit BG and tumor growth. In designing our diets, we wanted to avoid NCKDs [no calorie ketogenic diets] because of the difficulty in achieving long-term compliance with no CHO diets in potential future human studies and because Masko and colleagues recently reported that a 10% or 20% CHO diet slows tumor growth as effectively as NCKDs. Following early studies with 8% CHO diets, using 10% and 15% CHO, high protein diets in which 70% of the CHO was in the form of amylose, we found that, compared with a Western diet, they were indeed capable of reducing BG, insulin, and lactate levels and, importantly, in slowing the growth of implanted murine and human tumors, with little or no effects on mouse weight.”

There is good reason to apply these finding to human case management:

“Consistent with the notion that reducing BG in humans can be beneficial, there is a wealth of epidemiologic evidence showing a clear association between BG and/or insulin levels (which are determined by BG levels) and the incidence of human cancers. Thus, although our studies were conducted, out of necessity, with mice, the fact that human BG can be significantly reduced with low CHO diets and the association of many cancers with high BG levels suggest that our findings are very likely relevant to human cancers as well, particularly in cancers that have been associated with higher baseline BG and/or insulin levels, such as pancreatic, breast, colorectal, endometrial, and esophageal cancers.”

This also has application to prostate cancers:

“In addition to these cancers, a low CHO diet may also be beneficial in early-stage prostate cancer, even though it is not typically detectable by PET. This is because the metastases of these tumors kill the patients and, given the pivotal role of lactate in promoting metastasis, our low CHO diets could significantly reduce metastasis by reducing tumor-associated lactate levels.”

Regarding concerns about the impact on kidney function…

“In terms of macronutrient composition, even though high protein has been shown to promote satiety—thus reducing obesity, BG, and insulin levels—and enhance both antitumor immunity, through amino acid supplementation, and life span, we were concerned, based on the literature, that high protein levels might cause kidney damage. More recent data, however, suggest that this may only occur in individuals with existing chronic kidney disease and that in normal people, the increase in glomerular filtration rate and kidney cellularity that occur with long-term high protein consumption may be a normal response.”

Incidentally, amylose starch prevents DNA damage in the colon that may otherwise be caused by red meat:

“Interestingly, colonic cancer-inducing damage caused by red meats may be avoided with high amylose, low CHO diets. These studies suggest that macronutrient sources and combinations are very important…”

The authors conclude:

“Our study, herein, shows that a high amylose containing low CHO, high protein diet reduces BG, insulin, and glycolysis, slows tumor growth, reduces tumor incidence, and works additively with existing therapies without weight loss or kidney failure. Such a diet, therefore, has the potential of being both a novel cancer prophylactic and treatment, warranting further investigation of its applicability in the clinic, especially in combination with existing therapies.”

Regarding weight loss, what if exercise is added to the program? Will high protein still beat high carbohydrate. A study published in the journal The Physician and Sports Medicine studies this question as the authors set out to…

“…determine whether sedentary obese women with elevated levels of homeostatic model assessment (HOMA) insulin resistance (ie, > 3.5) experience greater benefits from an exercise + higher-carbohydrate (HC) or carbohydrate-restricted weight loss program than women with lower HOMA levels.”

221 women who participated in a 10-week supervised exercise and weight loss program were assigned low-fat (30%) diets that consisted of 1200 kcals per day for 1 week (phase 1) and 1600 kcals per day for 9 weeks (phase 2) with either high carbohydrate (HC) or higher protein (HP). Fasting blood samples, body composition, anthropometry, resting energy expenditure, and fitness measurements were obtained at the beginning and end. Again we see high protein win out over high carbohydrate:

“Subjects in the HP group experienced greater weight loss (−4.4 ± 3.6 kg vs −2.6 ± 2.9 kg), fat loss (−3.4 ± 2.7 kg vs −1.7 ± 2.0 kg), reductions in serum glucose (3% vs 2%), and decreases in serum leptin levels (−30.8% vs −10.8%) than those in the HC group.”

The authors conclude:

“A carbohydrate-restricted diet promoted more favorable changes in weight loss, fat loss, and markers of health in obese women who initiated an exercise program compared with a diet higher in carbohydrate. Additionally, obese women who initiated training and dieting with higher HOMA levels experienced greater reductions in blood glucose following an HP diet.”

Regarding the use of vegetable or fruit juices in programs designed for weight loss, a study published in the journal Obesity demonstrates that this is counter-productive:

“Beverage consumption has been implicated in weight gain, but questions remain about the veracity of the association, whether the relationship is causal and what property of beverages is responsible. It was hypothesized that food form is the most salient attribute. Thus, a randomized controlled trial of food form was conducted. Energy-matched beverage or solid forms of fruits and vegetables were provided to 34, lean or overweight/obese adults for two 8-week periods with a 3-week washout interspersed.”

During the solid food arm of the study the lean group had no significant weight change while the overweight/obese group had weight gain, but during the juice phase…

“In contrast, incomplete dietary compensation and weight gain occurred in both the lean (43%) and overweight/obese (61%) groups during the beverage arm…These data demonstrate energy consumed as beverages may be especially problematic for weight gain.”

And for the carbohydrates that are consumed, a curious study also published in Obesity offers evidence that eating them mainly at dinner further aids in weight loss, satiety and more:

“This study was designed to investigate the effect of a low-calorie diet with carbohydrates eaten mostly at dinner on anthropometric, hunger/satiety, biochemical, and inflammatory parameters. Hormonal secretions were also evaluated. Seventy-eight police officers (BMI >30) were randomly assigned to experimental (carbohydrates eaten mostly at dinner) or control weight loss diets for 6 months. On day 0, 7, 90, and 180 blood samples and hunger scores were collected every 4 h from 0800 to 2000 hours. Anthropometric measurements were collected throughout the study.”

Amazingly…

“Greater weight loss, abdominal circumference, and body fat mass reductions were observed in the experimental diet in comparison to controls. Hunger scores were lower and greater improvements in fasting glucose, average daily insulin concentrations, and homeostasis model assessment for insulin resistance (HOMAIR), T-cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) levels were observed in comparison to controls. The experimental diet modified daily leptin and adiponectin concentrations compared to those observed at baseline and to a control diet.”

Wow…all that just from shifting carbohydrates to dinner. The authors conclude:

“A simple dietary manipulation of carbohydrate distribution appears to have additional benefits when compared to a conventional weight loss diet in individuals suffering from obesity. It might also be beneficial for individuals suffering from insulin resistance and the metabolic syndrome.”

The scientific data addressing various aspects of dietary fat is treated in a separate post, but it’s suitable here to consider a study published in The Journal of Clinical Endocrinology & Metabolism offering evidence that a low carbohydrate diet is equivalent to a low fat diet for weight loss:

“Overweight and obese men and women (24–61 yr of age) were recruited into a randomized trial to compare the effects of a low-fat (LF) vs. a low-carbohydrate (LC) diet on weight loss…Subjects on the LF diet consumed an average of 17.8% of energy from fat, compared with their habitual intake of 36.4%, and had a resulting energy restriction of 2540 kJ/d [585 calories]. Subjects on the LC diet consumed an average of 15.4% carbohydrate, compared with habitual intakes of about 50% carbohydrate, and had a resulting energy restriction of 3195 kJ/d [763 calories].”

At the end of the study period the LC group lost as much weight and had better insulin regulation:

“Both groups of subjects had significant weight loss over the 10 wk of diet intervention and nearly identical improvements in body weight and fat mass. LF subjects lost an average of 6.8 kg and had a decrease in body mass index of 2.2 kg/m2, compared with a loss of 7.0 kg and decrease in body mass index of 2.1 kg/m2 in the LC subjects. The LF group better preserved lean body mass when compared with the LC group; however, only the LC group had a significant decrease in circulating insulin concentrations.”

The authors conclude:

“”These data suggest that energy restriction achieved by a very LC diet is equally effective as a LF diet strategy for weight loss and decreasing body fat in overweight and obese adults.”

Bottom line: When designing a dietary strategy for weight loss and maintenance the individual patient’s functional and genetic constitution must be carefully considered (inflammation, immune regulation, insulin sensitivity, allergy, intestinal permeability, sleep disordered breathing and hormonal function are fundamentals); but there is an accumulation of evidence suggesting that a high protein, low carbohydrate regimen is a good starting point.