Nutrition assessment is the collection, integration, and analysis of nutrition-related data in order to craft a nutrition diagnosis that calls for an individualized intervention. It is the first step of the NCP and involves collecting, verifying, interpreting, and documenting key data necessary to identify nutrition-related problems [20]. The NCP has five assessment domains: (1) food- and nutrition-related history; (2) anthropometric measurements; (3) biochemical data, medical tests, and procedures; (4) nutrition-focused physical findings; and (5) client history. These data are usually available in any healthcare setting, and sources include the patient and family interview; food, beverage, medication, and activity logs; medical record; referring provider(s); and nutrition-related physical assessment.

The patient interview may be the best source of information related to the patient’s food and nutrition history. The RDN assesses the patient’s past and present food intake, factors that influence food intake (such as food security, access to cooking and food storage facilities, transportation, dentition, and cultural and religious observances), and food and nutrition knowledge. The RDN may collect dietary data from the patient via detailed, multiple-day diet records, a 24-h dietary recall (asking the patient to recall everything he/she ate or drank in the last 24 h), a brief diet history (querying about usual dietary patterns, food frequency, and food propensity), or a food screener or food frequency questionnaire (FFQ). While there are an abundance of validated FFQs available for use, their accuracy in assessing the intake of specific nutrients and dietary habits has been questioned [21]. FFQs and food screeners may be appropriate in identifying patients whose medical and nutritional needs are more complex and who would benefit from the involvement of a RDN to obtain and interpret their dietary intake and nutritional risk factors. In addition to dietary assessment, the patient’s past medical history, surgical history, social history, and readiness to change are assessed.

In addition to the patient’s report, other critical data can be acquired from the patient’s medical record and from the referring provider. Pertinent information from these sources may include the following: anthropometric data, past and present medications, biochemical data, medical test results, relevant procedures, and documentation from past providers related to the present medical diagnosis. With patient permission, a nutrition-related physical assessment can reveal signs and symptoms of deficiency or malnutrition [22]. By reviewing all of these sources, the patient’s dietary intake and nutritional status can be adequately assessed.

The second step of the NCP is the nutrition diagnosis: the identification and labeling of a nutrition-related problem that can be treated independently. The purpose of the nutrition diagnosis is to link the findings from diet assessment with the manifestations or exacerbation of a disease or medical condition. A nutrition diagnosis is not a medical diagnosis. A medical diagnosis, usually made by a MD or other advanced practice medical provider, identifies a diseased organ or body system or an aberrant metabolic process that can be treated and/or prevented. A medical diagnosis does not change until the disease has resolved. A nutrition diagnosis identifies an aberrant dietary practice or habit that is contributory to a patient’s medical diagnosis. A nutrition diagnosis can change over time as the patient and/or his/her risk factors for disease progression or recurrence changes. Confirming the appropriate nutrition diagnosis is critical because it is the pathway to appropriate nutrition intervention and evaluation.

As earlier noted, the IDNT has terms for stating nutrition diagnoses related to food and/or nutrient intake, clinical diagnoses, and behavioral/environmental issues. The approved terminology supports identification of the three components of the nutrition diagnosis: problem, etiology, and signs and symptoms (PES) [20, 23, 24]. The “problem” is the diagnostic label that describes the patient’s response to a nutrition-related practice or habit. The “etiology” is the cause or related factors contributing to the problem. An example of the wedding of the problem to a nutrition-related etiology is “overweight/obesity related to excessive energy intake.” The “signs and symptoms” are the results or defining characteristics of the problem. These are objective data that are observed by the clinician. Examples may include a patient’s altered laboratory values, patient-reported information, and medical diagnosis. Upon diagnosing the problem, etiology, and signs and symptoms, the RDN can craft the PES statement. The final PES statement from the example above would be “Overweight/obesity related to excessive energy intake as evidenced by patient’s 24-hour dietary recall and BMI of 42.0.” The nutrition diagnosis is a pivotal step in the nutrition care process and guides the clinician to the appropriate intervention.

An intervention is a purposeful series of events aimed at addressing a problem. Nutrition interventions are designed with the primary intent of improving or correcting the problem declared in the diagnostic PES statement. This third step of the NCP includes the selection, planning, and implementation of specific actions to address the problem or nutrition diagnosis. The nutrition intervention typically includes strategies by which patients may achieve the goals of the intervention and, in that sense, provides the foundation for measuring and evaluating nutrition-related outcomes over time. The patient and his/her family are always at the center of successful nutrition interventions. In designing and implementing the nutrition intervention, the RDN collaborates with the patient, the patient’s family, and/or other members of the healthcare team as needed to ameliorate the nutrition-related problem or signs and symptoms that result from the problem.

The nutrition intervention includes the identification and implementation of the appropriate therapeutic approach. The MNT appropriate for the primary problem, or diagnosis, is determined by using evidence-based nutrition guidelines, relevant research, and current clinical guidelines. The Academy created and manages an Evidence Analysis Library (EAL) [10] and three nutrition care manuals, each containing the most up-to-date information regarding nutrition-related diseases and conditions. The Academy’s EAL is available for use at www.​andeal.​org. The nutrition care manuals are updated regularly and contain content for normal nutrition as well as for acute and chronic diseases states for adult and pediatric populations. The third nutrition care manual is specific to sports nutrition.

The implementation of the intervention may include patient education materials (nutrition education), strategies and ideas for how to make the recommended changes, and tools for implementing and complying with the intervention. The development of the intervention is grounded in behavior change theory (nutrition counseling) as deemed appropriate for each patient [25–30]. It is thus highly individualized per patient factors, such as motivation and enthusiasm to change, educational needs, and learning style. Productive nutrition education delivery is patient and family centered as the success of the intervention hinges on the involvement of the patient in his/her own care [25–28]. In an effort to enhance the patient’s involvement or compliance with the intervention, two counseling approaches used by RDNs are cognitive behavioral therapy and motivational interviewing. Cognitive behavioral therapy is counseling that is focused on identifying the mental and emotional relationships between thoughts, feelings, and behaviors that are related to a specific dietary practice or habit [29, 30]. Motivational interviewing is a nonjudgmental and non-confrontational counseling approach that is aimed at increasing patients’ awareness of the necessity for specific changes while guiding them through the stages of change [30].

Documentation of the nutrition intervention  – its effects on the patient as well as on his/her disease process – is an ongoing process, especially if the patient is seen in follow-up on a regular or serial basis and if modifications to the initial MNT are needed. Documentation of MNT includes date and time of intervention; treatment goals, patient-stated goals, and expected outcomes; patient receptivity and readiness to change; resources utilized; and recommended interventions and/or topics of education for further follow-up.

The results of the nutrition intervention on the targeted problem(s) must be evaluated for its effectiveness. If the intervention was ineffective in managing the problem intended, the reasons for its failure should be evaluated and corrected. Thus, the fourth and final step of the nutrition care process is monitoring and evaluation. Monitoring is the review and measurement of the patient’s nutritional status and response to MNT over time, whereas evaluation is the comparison of present findings to previous. This step has three interrelated processes: (1) monitor progress (monitoring), (2) measure outcomes (reassessment), and (3) evaluate outcomes (evaluation) [23, 24].